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• Tension between the dependency inversion principle and avoiding "new" in C++?

  - by Kazark

  I have seen a lot of advice that it is better to do Type object; than Type* object = new Type(); in C++ whenever possible. I understand the rational behind this and appreciate it. But according to my understanding, to practice dependency inversion requires pointers, e.g.: Type* object = new Implementation();. (Or am I wrong about that?) Is there an inherent tension between the DIP and avoiding new when using C++? If so, what patterns/principles/practices can be used to mitigate this tension?

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• Material tiling and offset in unity

  - by Simran kaur

  Ambiguity: What exactly is the difference between Tiling the material and Offset of material? Need to do: I need the material to be repeated n times on the object where I need to set the value of n via script.How do I do it? It seems to happen through Tiling(tried via inspector) but again what is difference between mainTextureOffset and setTextureOffset? Tried: Following is the line of code that I tried to repeat the texture n number of times on an object(repeat across the width of object), but it does nothing significant that I can see.

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• Tester/Doer pattern: Assume the caller conforms to the pattern or be defensive and repeat the check?

  - by Daniel Hilgarth

  Assume a simple class that implements the Tester/Doer pattern: public class FooCommandHandler : ICommandHandler { public bool CanHandle(object command) { return command is FooCommand; } public void Handle(object command) { var fooCommand = (FooCommand)command; // Do something with fooCommand } } Now, if someone doesn't conform to the pattern and calls Handle without verifying the command via CanHandle, the code in Handle throws an exception. However, depending on the actual implementation of Handle this can be a whole range of different exceptions. The following implementation would check CanHandle again in Handle and throw a descriptive exception: public void Handle(object command) { if(!CanHandle(command)) throw new TesterDoerPatternUsageViolationException("Please call CanHandle first"); // actual implementation of handling the command. } This has the advantage that the exception is very descriptive. It has the disadvantage that CanHandle is called twice for "good" clients. Is there a consensus on which variation should be used?

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• YouTube fullscreen not displaying

  - by pt2ph8

  For some reason YouTube videos in my website do not get the fullscreen button, even if I added the parameter allowFullScreen set to true both in the object and embed tag. Here's an example page: http://www.indievault.it/2011/11/09/indie-vault-alla-games-week-2011-online-la-video-gallery/ Just take a quick look at the source. The allowFullScreen param is there, but the button won't show. Here's an excerpt from the code in that page: <object width="540" height="325"><param name="movie" value="http://www.youtube.com/v/dvYQhJwwkgA"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/dvYQhJwwkgA" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="540" height="325"></embed </object>

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• Exchange 2010 Deployment Notes &ndash; iPhone and Exchange ActiveSync issue

  - by BWCA

  After we moved one of our user mailboxes from Exchange 2003 to 2010, the user started getting a Cannot get mail. The connection to the server failed error message on their iPhone device. There are a lot of references on Google to check for inherited permissions to resolve the error message.  We quickly determined that we were not dealing with a permissions issue. After some additional troubleshooting and research, we were able to isolate the problem to a device partnership issue. To resolve the issue, use ADSI Edit to find the user object. When you find the user object, double-click on it and you should see a CN=ExchangeActiveSyncDevices container under the user object as shown below.  On the right-hand side, you should see one or more device partnerships.   Right-click the device partnership according to the device the user is using, and click Delete. After you remove the device partnership, please wait until Active Directory replication completes before you set up the device again.

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• Randomly spawning bitmaps on cnvas

  - by Toystoj

  I need some ideas in order to finish algorithm. I'm randomly placing objects (bitmaps) on canvas without overlapping. Time needed to finish it is my problem. When I need to spawn for example 80% of canvas it takes to long. So i was thinking : I should make some change when the bitmaps take off 50 % of canvas. I want to tell algorithm that it should generate new locations (x,y) where it is free space. My question is : How to render new location (x,y) in place where is free space. In summary: Things I know : object location (x,y) 4 corners (x,y) of object object width, height canvas width, height Any suggestions?

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• How do I swap two objects in a GC language without triggering GC?

  - by TenFour04

  I have two array lists. that I want to swap each frame. My question is, does the variable 'temp' need to be a member variable to avoid triggering GC, assuming this method is called on dozens of objects each frame? I'm not creating a new object, just a new reference to an object. public void LateUpdate(){ ArrayList<int> temp = previousFrameCollisions; previousFrameCollisions = currentFrameCollisions; currentFrameCollisions = temp; currentFrameCollisions.clear(); } I've been told there's no reason to make a primitive into a member variable just to avoid GC, so my best guess is that this also applies to object references.

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• JavaScript: scroll position (Webkit engine) [migrated]

  - by Julien

  I'm currently trying to use JavaScript to find out how far down the page the user has scrolled; for Firefox 8.0, the keyword is pageYOffset. To say things mechanically: The page has a certain height. In Firefox, the useful object is document.documentElement.scrollHeight. The browser's visible area also has a certain height. In Firefox, the object is window.innerHeight; in IE8, document.documentElement.clientHeight. I need to know where the user is in the page vertically; in other words, how many pixels down the page the user has scrolled. Does Webkit have a DOM object that refers to the current scroll position? Thank you.

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• libgdx - collision detection with tiled map java

  - by user2875021

  currently, I am working on a 2d rpg game which is similar to final fantasy 1-4. I can load up a tiled map and the sprite can walk freely on the map. However, I will like to create a wall for it to stop walking through it. I created three tiled layer Background, Collision, Overhead and one Collision object layer with rectangles only. "How do I handle collisions with the object layer in the tiled map?" "Do I have to create every single rectangle that is in the object layer with Rectangle rectangle = new Rectangle() and rectangle.set(x, y, width, height)in the code?" Thank you very much in advance. Any help is greatly appreciated!

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• Synchronized Property Changes (Part 4)

  - by Geertjan

  The next step is to activate the undo/redo functionality... for a Node. Something I've not seen done before. I.e., when the Node is renamed via F2 on the Node, the "Undo/Redo" buttons should start working. Here is the start of the solution, via this item in the mailing list and Timon Veenstra's BeanNode class, note especially the items in bold: public class ShipNode extends BeanNode implements PropertyChangeListener, UndoRedo.Provider { private final InstanceContent ic; private final ShipSaveCapability saveCookie; private UndoRedo.Manager manager; private String oldDisplayName; private String newDisplayName; private Ship ship; public ShipNode(Ship bean) throws IntrospectionException { this(bean, new InstanceContent()); } private ShipNode(Ship bean, InstanceContent ic) throws IntrospectionException { super(bean, Children.LEAF, new ProxyLookup(new AbstractLookup(ic), Lookups.singleton(bean))); this.ic = ic; setDisplayName(bean.getType()); setShortDescription(String.valueOf(bean.getYear())); saveCookie = new ShipSaveCapability(bean); bean.addPropertyChangeListener(WeakListeners.propertyChange(this, bean)); } @Override public Action[] getActions(boolean context) { List<? extends Action> shipActions = Utilities.actionsForPath("Actions/Ship"); return shipActions.toArray(new Action[shipActions.size()]); } protected void fire(boolean modified) { if (modified) { ic.add(saveCookie); } else { ic.remove(saveCookie); } } @Override public UndoRedo getUndoRedo() { manager = Lookup.getDefault().lookup( UndoRedo.Manager.class); return manager; } private class ShipSaveCapability implements SaveCookie { private final Ship bean; public ShipSaveCapability(Ship bean) { this.bean = bean; } @Override public void save() throws IOException { StatusDisplayer.getDefault().setStatusText("Saving..."); fire(false); } } @Override public boolean canRename() { return true; } @Override public void setName(String newDisplayName) { Ship c = getLookup().lookup(Ship.class); oldDisplayName = c.getType(); c.setType(newDisplayName); fireNameChange(oldDisplayName, newDisplayName); fire(true); fireUndoableEvent("type", ship, oldDisplayName, newDisplayName); } public void fireUndoableEvent(String property, Ship source, Object oldValue, Object newValue) { ReUndoableEdit reUndoableEdit = new ReUndoableEdit( property, source, oldValue, newValue); UndoableEditEvent undoableEditEvent = new UndoableEditEvent( this, reUndoableEdit); manager.undoableEditHappened(undoableEditEvent); } private class ReUndoableEdit extends AbstractUndoableEdit { private Object oldValue; private Object newValue; private Ship source; private String property; public ReUndoableEdit(String property, Ship source, Object oldValue, Object newValue) { super(); this.oldValue = oldValue; this.newValue = newValue; this.source = source; this.property = property; } @Override public void undo() throws CannotUndoException { setName(oldValue.toString()); } @Override public void redo() throws CannotRedoException { setName(newValue.toString()); } } @Override public String getDisplayName() { Ship c = getLookup().lookup(Ship.class); if (null != c.getType()) { return c.getType(); } return super.getDisplayName(); } @Override public String getShortDescription() { Ship c = getLookup().lookup(Ship.class); if (null != String.valueOf(c.getYear())) { return String.valueOf(c.getYear()); } return super.getShortDescription(); } @Override public void propertyChange(PropertyChangeEvent evt) { if (evt.getPropertyName().equals("type")) { String oldDisplayName = evt.getOldValue().toString(); String newDisplayName = evt.getNewValue().toString(); fireDisplayNameChange(oldDisplayName, newDisplayName); } else if (evt.getPropertyName().equals("year")) { String oldToolTip = evt.getOldValue().toString(); String newToolTip = evt.getNewValue().toString(); fireShortDescriptionChange(oldToolTip, newToolTip); } fire(true); } } Undo works when rename is done, but Redo never does, because Undo is constantly activated, since it is reactivated whenever there is a name change. And why must the UndoRedoManager be retrieved from the Lookup (it doesn't work otherwise)? Don't get that part of the code either. Help welcome!

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• Collisions and Lists

  - by user50635

  I've run into an issue that breaks my collisions. Here's my method: Gather Input Project Rectangle Check for intersection and ispassable Update The update method is built on object_position * seconds_passed * velocity * speed. Input changes velocity and is normalized if 1. This method works well with just one object comparison, however I pass a list or a for loop to the collision detector and velocity gets changed back to a non zero when the list hits an object that passes the test and the object can pass through. Any solutions would be much appreciated. Side note is there a more proper way to simulate movement?

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• Moving from mock to real objects?

  - by jjchiw

  I'm like doing TDD so I started everything mocking objects, creating interface, stubbing, great. The design seems to work, now I'll implement the stuff, a lot of the code used in the stubs are going to be reused in my real implementation yay! Now should I duplicate the tests to use the real object implementation (but keeping the mocks object of the sensitive stuff like Database and "services" that are out of my context (http calls, etc...)) Or just change the mocks and stubs of the actual tests to use the real objects....... So the question is that, keep two tests or replace the stubs, mocks? And after that, I should keep designing with the mocks, stubs or just go with real objects? (Just making myself clear I'll keep the mock object of the sensitive stuff like database and services that are out of my context, in both situations.)

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• How do I swap two objects in C# (specifically Mono) without triggering GC?

  - by TenFour04

  I have two array lists. that I want to swap each frame. My question is, does the variable 'temp' need to be a member variable to avoid triggering GC, assuming this method is called on dozens of objects each frame? I'm not creating a new object, just a new reference to an object. public void LateUpdate(){ ArrayList<int> temp = previousFrameCollisions; previousFrameCollisions = currentFrameCollisions; currentFrameCollisions = temp; currentFrameCollisions.clear(); } I've been told there's no reason to make a primitive into a member variable just to avoid GC, so my best guess is that this also applies to object references.

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• How can I make my generic comparer (IComparer) handle nulls? [closed]

  - by Nick G

  Hi, I'm trying to write a generic object comparer for sorting, but I have noticed it does not handle the instance where one of the values it's comparing is null. When an object is null, I want it to treat it the same as the empty string. I've tried setting the null values to String.Empty but then I get an error of "Object must be of type String" when calling CompareTo() on it. public int Compare(T x, T y) { PropertyInfo propertyInfo = typeof(T).GetProperty(sortExpression); IComparable obj1 = (IComparable)propertyInfo.GetValue(x, null); IComparable obj2 = (IComparable)propertyInfo.GetValue(y, null); if (obj1 == null) obj1 = String.Empty; // This doesn't work! if (obj2 == null) obj2 = String.Empty; // This doesn't work! if (SortDirection == SortDirection.Ascending) return obj1.CompareTo(obj2); else return obj2.CompareTo(obj1); } I'm pretty stuck with this now! Any help would be appreciated.

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• SQL Server Requery() sometimes hangs

  - by PSU

  I have an issue with Visual C++ and Microsoft SQL Server 2008R2. The following code will occasionally hang: Object->Update(); if(Object->CanRestart()) { //Why does this not return?? m_pDBRoRBaseObject->Requery(); } Object is derived from CRecordset. It looks to me as though a call to ::SQLExecute(m_hstmt) in the Requery() method is hanging, but I can't (with my current skill set anyway) figure out a way around this. Has anyone had a similar problem, or an insight of any sort?

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• How can I find the closest vector to another in a specific direction?

  - by Sniper

  Perhaps I am not phrasing it incorrectly in my searches, but I can not find anything on this. I have a vector3 with a specific direction that it is facing, I want to get the closest object to that position in that specific direction. Basically I want to get the object that is being aimed at. I have thought about finding all objects within a box and then finding the closest object to my vector from them results, but I am sure that there is a more efficient way. The Z axis is optional, the objects are most likely within a few meters of the search vector. http://i.stack.imgur.com/FafAu.jpg

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• Creating a dynamic proxy generator – Part 1 – Creating the Assembly builder, Module builder and cach

  - by SeanMcAlinden

  I’ve recently started a project with a few mates to learn the ins and outs of Dependency Injection, AOP and a number of other pretty crucial patterns of development as we’ve all been using these patterns for a while but have relied totally on third part solutions to do the magic. We thought it would be interesting to really get into the details by rolling our own IoC container and hopefully learn a lot on the way, and you never know, we might even create an excellent framework. The open source project is called Rapid IoC and is hosted at http://rapidioc.codeplex.com/ One of the most interesting tasks for me is creating the dynamic proxy generator for enabling Aspect Orientated Programming (AOP). In this series of articles, I’m going to track each step I take for creating the dynamic proxy generator and I’ll try my best to explain what everything means - mainly as I’ll be using Reflection.Emit to emit a fair amount of intermediate language code (IL) to create the proxy types at runtime which can be a little taxing to read. It’s worth noting that building the proxy is without a doubt going to be slightly painful so I imagine there will be plenty of areas I’ll need to change along the way. Anyway lets get started…   Part 1 - Creating the Assembly builder, Module builder and caching mechanism Part 1 is going to be a really nice simple start, I’m just going to start by creating the assembly, module and type caches. The reason we need to create caches for the assembly, module and types is simply to save the overhead of recreating proxy types that have already been generated, this will be one of the important steps to ensure that the framework is fast… kind of important as we’re calling the IoC container ‘Rapid’ – will be a little bit embarrassing if we manage to create the slowest framework. The Assembly builder The assembly builder is what is used to create an assembly at runtime, we’re going to have two overloads, one will be for the actual use of the proxy generator, the other will be mainly for testing purposes as it will also save the assembly so we can use Reflector to examine the code that has been created. Here’s the code: DynamicAssemblyBuilder using System; using System.Reflection; using System.Reflection.Emit; namespace Rapid.DynamicProxy.Assembly {     /// <summary>     /// Class for creating an assembly builder.     /// </summary>     internal static class DynamicAssemblyBuilder     {         #region Create           /// <summary>         /// Creates an assembly builder.         /// </summary>         /// <param name="assemblyName">Name of the assembly.</param>         public static AssemblyBuilder Create(string assemblyName)         {             AssemblyName name = new AssemblyName(assemblyName);               AssemblyBuilder assembly = AppDomain.CurrentDomain.DefineDynamicAssembly(                     name, AssemblyBuilderAccess.Run);               DynamicAssemblyCache.Add(assembly);               return assembly;         }           /// <summary>         /// Creates an assembly builder and saves the assembly to the passed in location.         /// </summary>         /// <param name="assemblyName">Name of the assembly.</param>         /// <param name="filePath">The file path.</param>         public static AssemblyBuilder Create(string assemblyName, string filePath)         {             AssemblyName name = new AssemblyName(assemblyName);               AssemblyBuilder assembly = AppDomain.CurrentDomain.DefineDynamicAssembly(                     name, AssemblyBuilderAccess.RunAndSave, filePath);               DynamicAssemblyCache.Add(assembly);               return assembly;         }           #endregion     } }   So hopefully the above class is fairly explanatory, an AssemblyName is created using the passed in string for the actual name of the assembly. An AssemblyBuilder is then constructed with the current AppDomain and depending on the overload used, it is either just run in the current context or it is set up ready for saving. It is then added to the cache.   DynamicAssemblyCache using System.Reflection.Emit; using Rapid.DynamicProxy.Exceptions; using Rapid.DynamicProxy.Resources.Exceptions;   namespace Rapid.DynamicProxy.Assembly {     /// <summary>     /// Cache for storing the dynamic assembly builder.     /// </summary>     internal static class DynamicAssemblyCache     {         #region Declarations           private static object syncRoot = new object();         internal static AssemblyBuilder Cache = null;           #endregion           #region Adds a dynamic assembly to the cache.           /// <summary>         /// Adds a dynamic assembly builder to the cache.         /// </summary>         /// <param name="assemblyBuilder">The assembly builder.</param>         public static void Add(AssemblyBuilder assemblyBuilder)         {             lock (syncRoot)             {                 Cache = assemblyBuilder;             }         }           #endregion           #region Gets the cached assembly                  /// <summary>         /// Gets the cached assembly builder.         /// </summary>         /// <returns></returns>         public static AssemblyBuilder Get         {             get             {                 lock (syncRoot)                 {                     if (Cache != null)                     {                         return Cache;                     }                 }                   throw new RapidDynamicProxyAssertionException(AssertionResources.NoAssemblyInCache);             }         }           #endregion     } } The cache is simply a static property that will store the AssemblyBuilder (I know it’s a little weird that I’ve made it public, this is for testing purposes, I know that’s a bad excuse but hey…) There are two methods for using the cache – Add and Get, these just provide thread safe access to the cache.   The Module Builder The module builder is required as the create proxy classes will need to live inside a module within the assembly. Here’s the code: DynamicModuleBuilder using System.Reflection.Emit; using Rapid.DynamicProxy.Assembly; namespace Rapid.DynamicProxy.Module {     /// <summary>     /// Class for creating a module builder.     /// </summary>     internal static class DynamicModuleBuilder     {         /// <summary>         /// Creates a module builder using the cached assembly.         /// </summary>         public static ModuleBuilder Create()         {             string assemblyName = DynamicAssemblyCache.Get.GetName().Name;               ModuleBuilder moduleBuilder = DynamicAssemblyCache.Get.DefineDynamicModule                 (assemblyName, string.Format("{0}.dll", assemblyName));               DynamicModuleCache.Add(moduleBuilder);               return moduleBuilder;         }     } } As you can see, the module builder is created on the assembly that lives in the DynamicAssemblyCache, the module is given the assembly name and also a string representing the filename if the assembly is to be saved. It is then added to the DynamicModuleCache. DynamicModuleCache using System.Reflection.Emit; using Rapid.DynamicProxy.Exceptions; using Rapid.DynamicProxy.Resources.Exceptions; namespace Rapid.DynamicProxy.Module {     /// <summary>     /// Class for storing the module builder.     /// </summary>     internal static class DynamicModuleCache     {         #region Declarations           private static object syncRoot = new object();         internal static ModuleBuilder Cache = null;           #endregion           #region Add           /// <summary>         /// Adds a dynamic module builder to the cache.         /// </summary>         /// <param name="moduleBuilder">The module builder.</param>         public static void Add(ModuleBuilder moduleBuilder)         {             lock (syncRoot)             {                 Cache = moduleBuilder;             }         }           #endregion           #region Get           /// <summary>         /// Gets the cached module builder.         /// </summary>         /// <returns></returns>         public static ModuleBuilder Get         {             get             {                 lock (syncRoot)                 {                     if (Cache != null)                     {                         return Cache;                     }                 }                   throw new RapidDynamicProxyAssertionException(AssertionResources.NoModuleInCache);             }         }           #endregion     } }   The DynamicModuleCache is very similar to the assembly cache, it is simply a statically stored module with thread safe Add and Get methods.   The DynamicTypeCache To end off this post, I’m going to create the cache for storing the generated proxy classes. I’ve spent a fair amount of time thinking about the type of collection I should use to store the types and have finally decided that for the time being I’m going to use a generic dictionary. This may change when I can actually performance test the proxy generator but the time being I think it makes good sense in theory, mainly as it pretty much maintains it’s performance with varying numbers of items – almost constant (0)1. Plus I won’t ever need to loop through the items which is not the dictionaries strong point. Here’s the code as it currently stands: DynamicTypeCache using System; using System.Collections.Generic; using System.Security.Cryptography; using System.Text; namespace Rapid.DynamicProxy.Types {     /// <summary>     /// Cache for storing proxy types.     /// </summary>     internal static class DynamicTypeCache     {         #region Declarations           static object syncRoot = new object();         public static Dictionary<string, Type> Cache = new Dictionary<string, Type>();           #endregion           /// <summary>         /// Adds a proxy to the type cache.         /// </summary>         /// <param name="type">The type.</param>         /// <param name="proxy">The proxy.</param>         public static void AddProxyForType(Type type, Type proxy)         {             lock (syncRoot)             {                 Cache.Add(GetHashCode(type.AssemblyQualifiedName), proxy);             }         }           /// <summary>         /// Tries the type of the get proxy for.         /// </summary>         /// <param name="type">The type.</param>         /// <returns></returns>         public static Type TryGetProxyForType(Type type)         {             lock (syncRoot)             {                 Type proxyType;                 Cache.TryGetValue(GetHashCode(type.AssemblyQualifiedName), out proxyType);                 return proxyType;             }         }           #region Private Methods           private static string GetHashCode(string fullName)         {             SHA1CryptoServiceProvider provider = new SHA1CryptoServiceProvider();             Byte[] buffer = Encoding.UTF8.GetBytes(fullName);             Byte[] hash = provider.ComputeHash(buffer, 0, buffer.Length);             return Convert.ToBase64String(hash);         }           #endregion     } } As you can see, there are two public methods, one for adding to the cache and one for getting from the cache. Hopefully they should be clear enough, the Get is a TryGet as I do not want the dictionary to throw an exception if a proxy doesn’t exist within the cache. Other than that I’ve decided to create a key using the SHA1CryptoServiceProvider, this may change but my initial though is the SHA1 algorithm is pretty fast to put together using the provider and it is also very unlikely to have any hashing collisions. (there are some maths behind how unlikely this is – here’s the wiki if you’re interested http://en.wikipedia.org/wiki/SHA_hash_functions)   Anyway, that’s the end of part 1 – although I haven’t started any of the fun stuff (by fun I mean hairpulling, teeth grating Relfection.Emit style fun), I’ve got the basis of the DynamicProxy in place so all we have to worry about now is creating the types, interceptor classes, method invocation information classes and finally a really nice fluent interface that will abstract all of the hard-core craziness away and leave us with a lightning fast, easy to use AOP framework. Hope you find the series interesting. All of the source code can be viewed and/or downloaded at our codeplex site - http://rapidioc.codeplex.com/ Kind Regards, Sean.

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• Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 3 – Table per Concrete Type (TPC) and Choosing Strategy Guidelines

  - by mortezam

  This is the third (and last) post in a series that explains different approaches to map an inheritance hierarchy with EF Code First. I've described these strategies in previous posts: Part 1 – Table per Hierarchy (TPH) Part 2 – Table per Type (TPT)In today’s blog post I am going to discuss Table per Concrete Type (TPC) which completes the inheritance mapping strategies supported by EF Code First. At the end of this post I will provide some guidelines to choose an inheritance strategy mainly based on what we've learned in this series. TPC and Entity Framework in the Past Table per Concrete type is somehow the simplest approach suggested, yet using TPC with EF is one of those concepts that has not been covered very well so far and I've seen in some resources that it was even discouraged. The reason for that is just because Entity Data Model Designer in VS2010 doesn't support TPC (even though the EF runtime does). That basically means if you are following EF's Database-First or Model-First approaches then configuring TPC requires manually writing XML in the EDMX file which is not considered to be a fun practice. Well, no more. You'll see that with Code First, creating TPC is perfectly possible with fluent API just like other strategies and you don't need to avoid TPC due to the lack of designer support as you would probably do in other EF approaches. Table per Concrete Type (TPC)In Table per Concrete type (aka Table per Concrete class) we use exactly one table for each (nonabstract) class. All properties of a class, including inherited properties, can be mapped to columns of this table, as shown in the following figure: As you can see, the SQL schema is not aware of the inheritance; effectively, we’ve mapped two unrelated tables to a more expressive class structure. If the base class was concrete, then an additional table would be needed to hold instances of that class. I have to emphasize that there is no relationship between the database tables, except for the fact that they share some similar columns. TPC Implementation in Code First Just like the TPT implementation, we need to specify a separate table for each of the subclasses. We also need to tell Code First that we want all of the inherited properties to be mapped as part of this table. In CTP5, there is a new helper method on EntityMappingConfiguration class called MapInheritedProperties that exactly does this for us. Here is the complete object model as well as the fluent API to create a TPC mapping: public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } }          public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } }          public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } }      public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; }              protected override void OnModelCreating(ModelBuilder modelBuilder)     {         modelBuilder.Entity<BankAccount>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("BankAccounts");         });         modelBuilder.Entity<CreditCard>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("CreditCards");         });                 } } The Importance of EntityMappingConfiguration ClassAs a side note, it worth mentioning that EntityMappingConfiguration class turns out to be a key type for inheritance mapping in Code First. Here is an snapshot of this class: namespace System.Data.Entity.ModelConfiguration.Configuration.Mapping {     public class EntityMappingConfiguration<TEntityType> where TEntityType : class     {         public ValueConditionConfiguration Requires(string discriminator);         public void ToTable(string tableName);         public void MapInheritedProperties();     } } As you have seen so far, we used its Requires method to customize TPH. We also used its ToTable method to create a TPT and now we are using its MapInheritedProperties along with ToTable method to create our TPC mapping. TPC Configuration is Not Done Yet!We are not quite done with our TPC configuration and there is more into this story even though the fluent API we saw perfectly created a TPC mapping for us in the database. To see why, let's start working with our object model. For example, the following code creates two new objects of BankAccount and CreditCard types and tries to add them to the database: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount();     CreditCard creditCard = new CreditCard() { CardType = 1 };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Running this code throws an InvalidOperationException with this message: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges. The reason we got this exception is because DbContext.SaveChanges() internally invokes SaveChanges method of its internal ObjectContext. ObjectContext's SaveChanges method on its turn by default calls AcceptAllChanges after it has performed the database modifications. AcceptAllChanges method merely iterates over all entries in ObjectStateManager and invokes AcceptChanges on each of them. Since the entities are in Added state, AcceptChanges method replaces their temporary EntityKey with a regular EntityKey based on the primary key values (i.e. BillingDetailId) that come back from the database and that's where the problem occurs since both the entities have been assigned the same value for their primary key by the database (i.e. on both BillingDetailId = 1) and the problem is that ObjectStateManager cannot track objects of the same type (i.e. BillingDetail) with the same EntityKey value hence it throws. If you take a closer look at the TPC's SQL schema above, you'll see why the database generated the same values for the primary keys: the BillingDetailId column in both BankAccounts and CreditCards table has been marked as identity. How to Solve The Identity Problem in TPC As you saw, using SQL Server’s int identity columns doesn't work very well together with TPC since there will be duplicate entity keys when inserting in subclasses tables with all having the same identity seed. Therefore, to solve this, either a spread seed (where each table has its own initial seed value) will be needed, or a mechanism other than SQL Server’s int identity should be used. Some other RDBMSes have other mechanisms allowing a sequence (identity) to be shared by multiple tables, and something similar can be achieved with GUID keys in SQL Server. While using GUID keys, or int identity keys with different starting seeds will solve the problem but yet another solution would be to completely switch off identity on the primary key property. As a result, we need to take the responsibility of providing unique keys when inserting records to the database. We will go with this solution since it works regardless of which database engine is used. Switching Off Identity in Code First We can switch off identity simply by placing DatabaseGenerated attribute on the primary key property and pass DatabaseGenerationOption.None to its constructor. DatabaseGenerated attribute is a new data annotation which has been added to System.ComponentModel.DataAnnotations namespace in CTP5: public abstract class BillingDetail {     [DatabaseGenerated(DatabaseGenerationOption.None)]     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } As always, we can achieve the same result by using fluent API, if you prefer that: modelBuilder.Entity<BillingDetail>()             .Property(p => p.BillingDetailId)             .HasDatabaseGenerationOption(DatabaseGenerationOption.None); Working With The Object Model Our TPC mapping is ready and we can try adding new records to the database. But, like I said, now we need to take care of providing unique keys when creating new objects: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount()      {          BillingDetailId = 1                          };     CreditCard creditCard = new CreditCard()      {          BillingDetailId = 2,         CardType = 1     };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Polymorphic Associations with TPC is Problematic The main problem with this approach is that it doesn’t support Polymorphic Associations very well. After all, in the database, associations are represented as foreign key relationships and in TPC, the subclasses are all mapped to different tables so a polymorphic association to their base class (abstract BillingDetail in our example) cannot be represented as a simple foreign key relationship. For example, consider the the domain model we introduced here where User has a polymorphic association with BillingDetail. This would be problematic in our TPC Schema, because if User has a many-to-one relationship with BillingDetail, the Users table would need a single foreign key column, which would have to refer both concrete subclass tables. This isn’t possible with regular foreign key constraints. Schema Evolution with TPC is Complex A further conceptual problem with this mapping strategy is that several different columns, of different tables, share exactly the same semantics. This makes schema evolution more complex. For example, a change to a base class property results in changes to multiple columns. It also makes it much more difficult to implement database integrity constraints that apply to all subclasses. Generated SQLLet's examine SQL output for polymorphic queries in TPC mapping. For example, consider this polymorphic query for all BillingDetails and the resulting SQL statements that being executed in the database: var query = from b in context.BillingDetails select b; Just like the SQL query generated by TPT mapping, the CASE statements that you see in the beginning of the query is merely to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type). TPC's SQL Queries are Union Based As you can see in the above screenshot, the first SELECT uses a FROM-clause subquery (which is selected with a red rectangle) to retrieve all instances of BillingDetails from all concrete class tables. The tables are combined with a UNION operator, and a literal (in this case, 0 and 1) is inserted into the intermediate result; (look at the lines highlighted in yellow.) EF reads this to instantiate the correct class given the data from a particular row. A union requires that the queries that are combined, project over the same columns; hence, EF has to pad and fill up nonexistent columns with NULL. This query will really perform well since here we can let the database optimizer find the best execution plan to combine rows from several tables. There is also no Joins involved so it has a better performance than the SQL queries generated by TPT where a Join is required between the base and subclasses tables. Choosing Strategy GuidelinesBefore we get into this discussion, I want to emphasize that there is no one single "best strategy fits all scenarios" exists. As you saw, each of the approaches have their own advantages and drawbacks. Here are some rules of thumb to identify the best strategy in a particular scenario: If you don’t require polymorphic associations or queries, lean toward TPC—in other words, if you never or rarely query for BillingDetails and you have no class that has an association to BillingDetail base class. I recommend TPC (only) for the top level of your class hierarchy, where polymorphism isn’t usually required, and when modification of the base class in the future is unlikely. If you do require polymorphic associations or queries, and subclasses declare relatively few properties (particularly if the main difference between subclasses is in their behavior), lean toward TPH. Your goal is to minimize the number of nullable columns and to convince yourself (and your DBA) that a denormalized schema won’t create problems in the long run. If you do require polymorphic associations or queries, and subclasses declare many properties (subclasses differ mainly by the data they hold), lean toward TPT. Or, depending on the width and depth of your inheritance hierarchy and the possible cost of joins versus unions, use TPC. By default, choose TPH only for simple problems. For more complex cases (or when you’re overruled by a data modeler insisting on the importance of nullability constraints and normalization), you should consider the TPT strategy. But at that point, ask yourself whether it may not be better to remodel inheritance as delegation in the object model (delegation is a way of making composition as powerful for reuse as inheritance). Complex inheritance is often best avoided for all sorts of reasons unrelated to persistence or ORM. EF acts as a buffer between the domain and relational models, but that doesn’t mean you can ignore persistence concerns when designing your classes. SummaryIn this series, we focused on one of the main structural aspect of the object/relational paradigm mismatch which is inheritance and discussed how EF solve this problem as an ORM solution. We learned about the three well-known inheritance mapping strategies and their implementations in EF Code First. Hopefully it gives you a better insight about the mapping of inheritance hierarchies as well as choosing the best strategy for your particular scenario. Happy New Year and Happy Code-Firsting! References ADO.NET team blog Java Persistence with Hibernate book a { color: #5A99FF; } a:visited { color: #5A99FF; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } .exception { background-color: #f0f0f0; font-style: italic; padding-bottom: 5px; padding-left: 5px; padding-top: 5px; padding-right: 5px; }

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• SQL Monitor’s data repository: Alerts

  - by Chris Lambrou

  In my previous post, I introduced the SQL Monitor data repository, and described how the monitored objects are stored in a hierarchy in the data schema, in a series of tables with a _Keys suffix. In this post I had planned to describe how the actual data for the monitored objects is stored in corresponding tables with _StableSamples and _UnstableSamples suffixes. However, I’m going to postpone that until my next post, as I’ve had a request from a SQL Monitor user to explain how alerts are stored. In the SQL Monitor data repository, alerts are stored in tables belonging to the alert schema, which contains the following five tables: alert.Alert alert.Alert_Cleared alert.Alert_Comment alert.Alert_Severity alert.Alert_Type In this post, I’m only going to cover the alert.Alert and alert.Alert_Type tables. I may cover the other three tables in a later post. The most important table in this schema is alert.Alert, as each row in this table corresponds to a single alert. So let’s have a look at it. SELECT TOP 100 AlertId, AlertType, TargetObject, [Read], SubType FROM alert.Alert ORDER BY AlertId DESC;  AlertIdAlertTypeTargetObjectReadSubType 165550397:Cluster,1,4:Name,s29:srp-mr03.testnet.red-gate.com,9:SqlServer,1,4:Name,s0:,10 265549387:Cluster,1,4:Name,s29:srp-mr03.testnet.red-gate.com,7:Machine,1,4:Name,s0:,10 365548187:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s15:FavouriteThings,00 465547157:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s15:FavouriteThings,00 565546147:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s15:FavouriteThings,00 665545187:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s14:SqlMonitorData,00 765544157:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s14:SqlMonitorData,00 865543147:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s14:SqlMonitorData,00 965542187:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s4:msdb,00 1065541147:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s4:msdb,00 11…     So what are we seeing here, then? Well, AlertId is an auto-incrementing identity column, so ORDER BY AlertId DESC ensures that we see the most recent alerts first. AlertType indicates the type of each alert, such as Job failed (6), Backup overdue (14) or Long-running query (12). The TargetObject column indicates which monitored object the alert is associated with. The Read column acts as a flag to indicate whether or not the alert has been read. And finally the SubType column is used in the case of a Custom metric (40) alert, to indicate which custom metric the alert pertains to. Okay, now lets look at some of those columns in more detail. The AlertType column is an easy one to start with, and it brings use nicely to the next table, data.Alert_Type. Let’s have a look at what’s in this table: SELECT AlertType, Event, Monitoring, Name, Description FROM alert.Alert_Type ORDER BY AlertType;  AlertTypeEventMonitoringNameDescription 1100Processor utilizationProcessor utilization (CPU) on a host machine stays above a threshold percentage for longer than a specified duration 2210SQL Server error log entryAn error is written to the SQL Server error log with a severity level above a specified value. 3310Cluster failoverThe active cluster node fails, causing the SQL Server instance to switch nodes. 4410DeadlockSQL deadlock occurs. 5500Processor under-utilizationProcessor utilization (CPU) on a host machine remains below a threshold percentage for longer than a specified duration 6610Job failedA job does not complete successfully (the job returns an error code). 7700Machine unreachableHost machine (Windows server) cannot be contacted on the network. 8800SQL Server instance unreachableThe SQL Server instance is not running or cannot be contacted on the network. 9900Disk spaceDisk space used on a logical disk drive is above a defined threshold for longer than a specified duration. 101000Physical memoryPhysical memory (RAM) used on the host machine stays above a threshold percentage for longer than a specified duration. 111100Blocked processSQL process is blocked for longer than a specified duration. 121200Long-running queryA SQL query runs for longer than a specified duration. 131400Backup overdueNo full backup exists, or the last full backup is older than a specified time. 141500Log backup overdueNo log backup exists, or the last log backup is older than a specified time. 151600Database unavailableDatabase changes from Online to any other state. 161700Page verificationTorn Page Detection or Page Checksum is not enabled for a database. 171800Integrity check overdueNo entry for an integrity check (DBCC DBINFO returns no date for dbi_dbccLastKnownGood field), or the last check is older than a specified time. 181900Fragmented indexesFragmentation level of one or more indexes is above a threshold percentage. 192400Job duration unusualThe duration of a SQL job duration deviates from its baseline duration by more than a threshold percentage. 202501Clock skewSystem clock time on the Base Monitor computer differs from the system clock time on a monitored SQL Server host machine by a specified number of seconds. 212700SQL Server Agent Service statusThe SQL Server Agent Service status matches the status specified. 222800SQL Server Reporting Service statusThe SQL Server Reporting Service status matches the status specified. 232900SQL Server Full Text Search Service statusThe SQL Server Full Text Search Service status matches the status specified. 243000SQL Server Analysis Service statusThe SQL Server Analysis Service status matches the status specified. 253100SQL Server Integration Service statusThe SQL Server Integration Service status matches the status specified. 263300SQL Server Browser Service statusThe SQL Server Browser Service status matches the status specified. 273400SQL Server VSS Writer Service statusThe SQL Server VSS Writer status matches the status specified. 283501Deadlock trace flag disabledThe monitored SQL Server’s trace flag cannot be enabled. 293600Monitoring stopped (host machine credentials)SQL Monitor cannot contact the host machine because authentication failed. 303700Monitoring stopped (SQL Server credentials)SQL Monitor cannot contact the SQL Server instance because authentication failed. 313800Monitoring error (host machine data collection)SQL Monitor cannot collect data from the host machine. 323900Monitoring error (SQL Server data collection)SQL Monitor cannot collect data from the SQL Server instance. 334000Custom metricThe custom metric value has passed an alert threshold. 344100Custom metric collection errorSQL Monitor cannot collect custom metric data from the target object. Basically, alert.Alert_Type is just a big reference table containing information about the 34 different alert types supported by SQL Monitor (note that the largest id is 41, not 34 – some alert types have been retired since SQL Monitor was first developed). The Name and Description columns are self evident, and I’m going to skip over the Event and Monitoring columns as they’re not very interesting. The AlertId column is the primary key, and is referenced by AlertId in the alert.Alert table. As such, we can rewrite our earlier query to join these two tables, in order to provide a more readable view of the alerts: SELECT TOP 100 AlertId, Name, TargetObject, [Read], SubType FROM alert.Alert a JOIN alert.Alert_Type at ON a.AlertType = at.AlertType ORDER BY AlertId DESC;  AlertIdNameTargetObjectReadSubType 165550Monitoring error (SQL Server data collection)7:Cluster,1,4:Name,s29:srp-mr03.testnet.red-gate.com,9:SqlServer,1,4:Name,s0:,00 265549Monitoring error (host machine data collection)7:Cluster,1,4:Name,s29:srp-mr03.testnet.red-gate.com,7:Machine,1,4:Name,s0:,00 365548Integrity check overdue7:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s15:FavouriteThings,00 465547Log backup overdue7:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s15:FavouriteThings,00 565546Backup overdue7:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s15:FavouriteThings,00 665545Integrity check overdue7:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s14:SqlMonitorData,00 765544Log backup overdue7:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s14:SqlMonitorData,00 865543Backup overdue7:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s14:SqlMonitorData,00 965542Integrity check overdue7:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s4:msdb,00 1065541Backup overdue7:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s4:msdb,00 Okay, the next column to discuss in the alert.Alert table is TargetObject. Oh boy, this one’s a bit tricky! The TargetObject of an alert is a serialized string representation of the position in the monitored object hierarchy of the object to which the alert pertains. The serialization format is somewhat convenient for parsing in the C# source code of SQL Monitor, and has some helpful characteristics, but it’s probably very awkward to manipulate in T-SQL. I could document the serialization format here, but it would be very dry reading, so perhaps it’s best to consider an example from the table above. Have a look at the alert with an AlertID of 65543. It’s a Backup overdue alert for the SqlMonitorData database running on the default instance of granger, my laptop. Each different alert type is associated with a specific type of monitored object in the object hierarchy (I described the hierarchy in my previous post). The Backup overdue alert is associated with databases, whose position in the object hierarchy is root → Cluster → SqlServer → Database. The TargetObject value identifies the target object by specifying the key properties at each level in the hierarchy, thus: Cluster: Name = "granger" SqlServer: Name = "" (an empty string, denoting the default instance) Database: Name = "SqlMonitorData" Well, look at the actual TargetObject value for this alert: "7:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s14:SqlMonitorData,". It is indeed composed of three parts, one for each level in the hierarchy: Cluster: "7:Cluster,1,4:Name,s7:granger," SqlServer: "9:SqlServer,1,4:Name,s0:," Database: "8:Database,1,4:Name,s14:SqlMonitorData," Each part is handled in exactly the same way, so let’s concentrate on the first part, "7:Cluster,1,4:Name,s7:granger,". It comprises the following: "7:Cluster," – This identifies the level in the hierarchy. "1," – This indicates how many different key properties there are to uniquely identify a cluster (we saw in my last post that each cluster is identified by a single property, its Name). "4:Name,s14:SqlMonitorData," – This represents the Name property, and its corresponding value, SqlMonitorData. It’s split up like this: "4:Name," – Indicates the name of the key property. "s" – Indicates the type of the key property, in this case, it’s a string. "14:SqlMonitorData," – Indicates the value of the property. At this point, you might be wondering about the format of some of these strings. Why is the string "Cluster" stored as "7:Cluster,"? Well an encoding scheme is used, which consists of the following: "7" – This is the length of the string "Cluster" ":" – This is a delimiter between the length of the string and the actual string’s contents. "Cluster" – This is the string itself. 7 characters. "," – This is a final terminating character that indicates the end of the encoded string. You can see that "4:Name,", "8:Database," and "14:SqlMonitorData," also conform to the same encoding scheme. In the example above, the "s" character is used to indicate that the value of the Name property is a string. If you explore the TargetObject property of alerts in your own SQL Monitor data repository, you might find other characters used for other non-string key property values. The different value types you might possibly encounter are as follows: "I" – Denotes a bigint value. For example, "I65432,". "g" – Denotes a GUID value. For example, "g32116732-63ae-4ab5-bd34-7dfdfb084c18,". "d" – Denotes a datetime value. For example, "d634815384796832438,". The value is stored as a bigint, rather than a native SQL datetime value. I’ll describe how datetime values are handled in the SQL Monitor data repostory in a future post. I suggest you have a look at the alerts in your own SQL Monitor data repository for further examples, so you can see how the TargetObject values are composed for each of the different types of alert. Let me give one further example, though, that represents a Custom metric alert, as this will help in describing the final column of interest in the alert.Alert table, SubType. Let me show you the alert I’m interested in: SELECT AlertId, a.AlertType, Name, TargetObject, [Read], SubType FROM alert.Alert a JOIN alert.Alert_Type at ON a.AlertType = at.AlertType WHERE AlertId = 65769;  AlertIdAlertTypeNameTargetObjectReadSubType 16576940Custom metric7:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s6:master,12:CustomMetric,1,8:MetricId,I2,02 An AlertType value of 40 corresponds to the Custom metric alert type. The Name taken from the alert.Alert_Type table is simply Custom metric, but this doesn’t tell us anything about the specific custom metric that this alert pertains to. That’s where the SubType value comes in. For custom metric alerts, this provides us with the Id of the specific custom alert definition that can be found in the settings.CustomAlertDefinitions table. I don’t really want to delve into custom alert definitions yet (maybe in a later post), but an extra join in the previous query shows us that this alert pertains to the CPU pressure (avg runnable task count) custom metric alert. SELECT AlertId, a.AlertType, at.Name, cad.Name AS CustomAlertName, TargetObject, [Read], SubType FROM alert.Alert a JOIN alert.Alert_Type at ON a.AlertType = at.AlertType JOIN settings.CustomAlertDefinitions cad ON a.SubType = cad.Id WHERE AlertId = 65769;  AlertIdAlertTypeNameCustomAlertNameTargetObjectReadSubType 16576940Custom metricCPU pressure (avg runnable task count)7:Cluster,1,4:Name,s7:granger,9:SqlServer,1,4:Name,s0:,8:Database,1,4:Name,s6:master,12:CustomMetric,1,8:MetricId,I2,02 The TargetObject value in this case breaks down like this: "7:Cluster,1,4:Name,s7:granger," – Cluster named "granger". "9:SqlServer,1,4:Name,s0:," – SqlServer named "" (the default instance). "8:Database,1,4:Name,s6:master," – Database named "master". "12:CustomMetric,1,8:MetricId,I2," – Custom metric with an Id of 2. Note that the hierarchy for a custom metric is slightly different compared to the earlier Backup overdue alert. It’s root → Cluster → SqlServer → Database → CustomMetric. Also notice that, unlike Cluster, SqlServer and Database, the key property for CustomMetric is called MetricId (not Name), and the value is a bigint (not a string). Finally, delving into the custom metric tables is beyond the scope of this post, but for the sake of avoiding any future confusion, I’d like to point out that whilst the SubType references a custom alert definition, the MetricID value embedded in the TargetObject value references a custom metric definition. Although in this case both the custom metric definition and custom alert definition share the same Id value of 2, this is not generally the case. Okay, that’s enough for now, not least because as I’m typing this, it’s almost 2am, I have to go to work tomorrow, and my alarm is set for 6am – eek! In my next post, I’ll either cover the remaining three tables in the alert schema, or I’ll delve into the way SQL Monitor stores its monitoring data, as I’d originally planned to cover in this post.

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• CodePlex Daily Summary for Tuesday, April 20, 2010

  CodePlex Daily Summary for Tuesday, April 20, 2010New ProjectsASP.NET MVC Extensibility: ASP.NET MVC Extensibility.ASP.NET MVC Starter: Tekpub's ASP.NET MVC 2.0 Starter Site, as put together by Rob Conery in Episode 15 of Mastering ASP.NET MVC (http://tekpub.com/production/starter)AzureDemo: An internal Azure demo and test bed for some projects. After demo is complete this project will be closed.Basic Sprite Sheet Creator: A basic c# program to create sprite sheets. CodeDefender: Protect your .Net codes easily with this smart obfuscator!Crawlr: Tema 2 projectDocument Session Manager - Visual Studio addin: Document Session Manager is a Visual Studio 2008 addin for saving and restoring the list of opened documents (xml files, source files, winforms, et...Esferatec.Text.RegularExpressions: assembly to build regular expression patternsFIFA World Cup 2010 Mobile Sticker Checklist: FIFA World Cup 2010 Mobile Sticker Checklist is a small application for Windows Mobile developed in CF 3.5 to keep tracking of your sticker album. ...Finia.net: 追忆 游乐网·幻之大地FusspawnsAI: Fusspawns UT AI is a small test engine for a classic ut remote bot api. intending to improve ut's ai to a god like level without cheating bots(bots...G.A.E.T.: This is a Graphical Asymmetric Encryption Tool based on R.S.A. algorithm with the help of Java Language.Even though, this may be a small applicatio...ItzyBitzySpider: Webcrawler project from computer science at UCN.JingQiao.Ads: My DDD NTier Architecture example project.Managed Meizu SDK Demo: In this project we are sharing the source code to demonstrate the usage of managed SDK for Meizu cell phones, currently for M8. With the help of th...MaxxUtils.MaxxTagger: MaxxTagger: An Mp3 Tag Editor.. Add /Edit/Remove MP3 ID3 V1 and 2.3 Tags like Title, Artist, Album, Album Art, Genre. Besides tag editing, it also ...Maya Project Management: The Maya Project Management is a clone of RedMine with all its functions and plug-in support, using the following technologies: Microsoft .net Fra...MessageBoxLib: A simple, robust library for Xbox 360 and Windows development using the XNA Game Studio that makes using the Guide class's message box functionalit...MyWSAT - ASP.NET Membership Administration Tool: MyWSAT aka ASP.NET WSAT is a WebForms based website Starter Kit for the ASP.NET Membership Provider. It is a feature rich application that takes ca...OntologyCreator: this is my thesis and it is not finished yetPOS for .Net Handheld Products Service Object: POS for .Net Service Object Handheld Products Bar Code ScannerPostBinder: PostBinder is a small helper library that deserializes ASP.NET requests into C# classes. This eliminates having to write repeated hand wiring co...PostSharp for ASP.NET Web Sites: Adds support for PostSharp 2.0 on ASP.NET Web Sites.Rapid Dictionary: * Rapid Dictionary is a Translation Dictionary initialized by language learning network http://wordsteps.com. * Dictionary developed in C# and Co...ROrganizer: If you feel your movie files are kept in messy way, try out the ROrganizer which helps you rearrange them.RoRoWoBlog: 萝萝窝个人博客开源项目SPGroupDeflector - Explicitly deny groups to webs within your Site Collection: Secure webs within your MOSS or WSS Portal by explicitly denying access to specific users in SharePoint groups.SSIS ShapeFileSource: SSIS ShapeFileSource imports ESRI Shapefiles, and the associated attribute file (.dbf). The component based on the free Shapefile C Library.StoreManagement: University assignment. The task is to build an application that can perform basic CRUD operations on a property and use an arbitrary database. ...Surfium: TODO ;-)TaskCleaner: This is a Windows Forms project created to kill some running process in order to enhace the performance of Windows execution. Sometimes it is desi...The Expert Calendar: The Expert Calendar is a MOSS 2007 webpart which allows to connect to a Event Item List and display event items in a small design customizable cale...Visual Studio Find Results Window Tweak: This is a Visual Studio 2010 add-in which enables you to adjust the format of the Find Results Window. It is written in C#, .NET 4.0 and requires ...Weightlifting Sinclair coeficient calculator: Weightlifting Sinclair coeficient calculator for competitors (for Windows Mobile platform)Windows Azure Web Storage Explorer: Windows Azure Web Storage Explorer makes it easier for developers to browse and manage Blobs, Queues and Tables from Windows Azure Storage account....New Releases#SNMP - C# Based Open Source SNMP for .NET and Mono: CatPaw (5.0) Beta 1: SNMP v3 support in snmpd is complete.ASP.Net MVC Crud with JqGrid: Mvc Crud with JqGrid 0.3.0: Fairly major reworking of the GenericDataGrid (with alot of work from James). Most noticeable is the replacing of Edit and Delete with action butt...Basic Sprite Sheet Creator: Sprite Tool v1.1: Fixed the progress bar, it now correctly displays text and progress. Also download will now come with an installer and an executable so you don't h...Basic Sprite Sheet Creator: Sprite Tool Version 1.0: Program used to make basic sprite sheets. please visit http://coderplex.blogspot.com for more infoBraintree Client Library: Braintree-1.2.1: Escape all XMLCodeDefender: CodeDefender v0.1: Protect your .Net exe and dll files with this smart tool.ColinTesting: test: testColinTesting: test2: test2ColinTesting: test3: test3ColinTesting: test4: test4ColinTesting: test6: test6CycleMania Starter Kit EAP - ASP.NET 4 Problem - Design - Solution: Cyclemania 0.08.63: See Source Code tab for recent change history.Document Session Manager - Visual Studio addin: Release v0.45948: Release v0.45948DotNetNuke® Community Edition: 05.04.00: Major Highlights Fixed issue where portal settings were not saved per portal. Fixed issue with importing page templates. Fixed issue with...DotNetNuke® Postgres Data Provider: DNN PG Provider 01.00.00 Beta2: Fixes problems with deprecated datatype money in Postgres. Upgrades DotnetNuke code base to 04.09.05 It comes with a patch for the DotNetNuke insta...FIFA World Cup 2010 Mobile Sticker Checklist: FIFA World Cup 2010 Mobile Sticker Checklist v0.1b: FIFA World Cup 2010 Mobile Sticker Checklist v0.1b First beta release. Requires Microsoft Compact Framework 3.5. It was tested on an HTC Touch Viva...FIFA World Cup 2010 Mobile Sticker Checklist: FIFA World Cup 2010 Mobile Sticker Checklist v0.2b: FIFA World Cup 2010 Mobile Sticker Checklist v0.2b Second beta release. Requires Microsoft Compact Framework 3.5. It was tested on an HTC Touch Viv...Fluent Ribbon Control Suite: Fluent Ribbon Control Suite 1.2: Fluent Ribbon Control Suite 1.2(supports .NET 3.5 and .NET 4 RTM) Includes: Fluent.dll (with .pdb and .xml) Showcase Application Samples Found...G.A.E.T.: Graphical Asymmetric Encryption Tool: User Interface The GAET User Interface is a window with five buttons. Each button is explained the following sections. Each button has a functional...HTML Ruby: 6.21.7: As long as I don't find anything else that I can improve, this will be submitted to Mozilla for review tomorrow. Added back process inserted conten...IBCSharp: IBCSharp 1.03: What IBCSharp 1.03.zip unzips to: http://i43.tinypic.com/24ffbqr.png Note: The above solution has MSTest, Typemock Isolator, and Microsoft CHESS c...LogikBug's IoC Container: Second Release: This project is dependent upon Microsoft.Practices.ServiceLocation and must be referenced when referencing LogikBug.Injection. Click here to view d...Managed Meizu SDK Demo: Library and Demo: Library and DemoMaxxUtils.MaxxTagger: MaxxUtils.MaxxTagger: Version: 1.0.0 (Beta) Instructions: Unzip the files to a folder and then dbl click on the exe. Known Issues: 1. When u copy or move a folde...OrthoLab: Cellule: Compile with Autodesk Maya 2008 32bit and 2010 64bit.OWASP Code Crawler: OWASP Code Crawler 2.7: Code Crawler 2.7 DescriptionIn terms of functionality there is not much new stuff in this release. We transplanted the new engine. Code Crawler is ...PerceptiveMCAPI - A .NET wrapper for the MailChimp Api: V1.2.3 PerceptiveMCAPI .Net Wrapper [Beta 2]: PerceptiveMCAPI – v 1.2.3 Change logFunctionality through MailChimp API announce v1.2.5 on 15-Feb-2010 .NET Wrapper New wrapper directives; api_Me...POS for .Net Handheld Products Service Object: POS for .Net Handhelp Products Service Object: The Service Object contained herein is a work in progress. This Service Object's is written as VS 2008 C# Project. The Target Platform is x86. ...PostSharp for ASP.NET Web Sites: R1: First release.Rich Ajax empowered Web/Cloud Applications: 6.4 beta 2c: A revisiov to the first fully featured version of Visual webGui offering web/cloud development tool that puts all ASP.NET Ajax limits behind with e...Should: Beta - 1.0: This is the initial release of the Should assertions extensions.Shrinkr: v1.0: First public release.Site Directory for SharePoint 2010 (from Microsoft Consulting Services, UK): v1.2: Address a bug found in v1.1 relating to the Delete Site Listings job not incrementing the 'Site Missing Count' for some SharePoint sites.Software Localization Tool: SharpSLT 1.0: New functions Backup before saving Delete entries Undo deletion Added more comments in the codeSPGroupDeflector - Explicitly deny groups to webs within your Site Collection: SPGroupDeflector: Download the source code, the wsp solution package, and Setup.docSSIS ShapeFileSource: Version 0.1: Short Preview of SSIS ShapeFileSource ComponentStarter Kit Mytrip.Mvc.Entity: Mytrip.Mvc.Entity 1.0: Warning Install MySql Connector/Net 6.3 MySQL Membership MSSQL Membership XML Membership UserManager FileManager Localization Captcha ...Surfium: Linux Expo Prebuild: First public releaseTaskCleaner: Initial Working Version: In this version we have all the features listed in the project description working fine. Built under Framework 3.5.Text to HTML: 0.4.5.0: CambiosSustitución de los siguientes caracteres: Anteriores: " < > ¡ © º ¿ Á Ä É Í Ñ Ó Ö Ú Ü ß á ä é í ñ ó ö ú ü € Nuevos: & ´ ≈ ¦ • ¸ ˆ ↓ ð … ∫ ...TS3QueryLib.Net: TS3QueryLib.Net Version 0.21.16.0: This release contains a bugfix for a bug that caused connection problems when connecting using an IP for some cases. So it's strongly recommended t...Tweety - Twitter Client: Tweety - 0.96: Form activation from system tray improved. General fixes. General code refactor.Web/Cloud Applications Development Framework | Visual WebGui: 6.4 Beta 2c: A revision to the first fully featured version of Visual webGui offering unique developer/designer interface and enhanced extensibility and customi...Windows Azure - PHP contributions: PhpAzureExtensions (Azure Drives) - 0.2.0: Extension for use with Windows Azure SDK 1.1! Breaking changes! Documentation can be found at http://phpazurecontrib.codeplex.com/wikipage?title=A...WoW Character Viewer: Viewer (40545): New setup build for 40545.Xrns2XMod: Xrns2XMod 0.0.5.3: Major Source code optimization: >> Separated logical code of xm/mod conversion from renoiseSong xml. Now all necessary renoise song data code is st...XsltDb - DotNetNuke XSLT module: 01.00.99: callable tag is introduced - create javascript ajax functions more easy import/export bug is fixed mdo:ajax checkbox processing is now the same...Most Popular ProjectsRawrWBFS ManagerSilverlight ToolkitAJAX Control ToolkitMicrosoft SQL Server Product Samples: DatabaseWindows Presentation Foundation (WPF)ASP.NETpatterns & practices – Enterprise LibraryPHPExcelMicrosoft SQL Server Community & SamplesMost Active ProjectsRawrpatterns & practices – Enterprise LibraryIndustrial DashboardIonics Isapi Rewrite FilterFarseer Physics EngineBlogEngine.NETPHPExcelCaliburn: An Application Framework for WPF and SilverlightNB_Store - Free DotNetNuke Ecommerce Catalog ModuleTweetSharp

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• CodePlex Daily Summary for Friday, April 06, 2012

  CodePlex Daily Summary for Friday, April 06, 2012Popular ReleasesBetter Explorer: Better Explorer 2.0.0.861 Alpha: - fixed new folder button operation not work well in some situations - removed some unnecessary code like subclassing that is not needed anymore - Added option to make Better Exlorer default (at least for WIN+E operations) - Added option to enable file operation replacements (like Terracopy) to work with Better Explorer - Added some basic usability to "Share" button - Other fixesLightFarsiDictionary - ??????? ??? ?????/???????: LightFarsiDictionary - v1: LightFarsiDictionary - v1WPF Application Framework (WAF): WPF Application Framework (WAF) 2.5.0.3: Version: 2.5.0.3 (Milestone 3): This release contains the source code of the WPF Application Framework (WAF) and the sample applications. Requirements .NET Framework 4.0 (The package contains a solution file for Visual Studio 2010) The unit test projects require Visual Studio 2010 Professional Changelog Legend: [B] Breaking change; [O] Marked member as obsolete [O] WAF: Mark the StringBuilderExtensions class as obsolete because the AppendInNewLine method can be replaced with string.Jo...Community TFS Build Extensions: April 2012: Release notes to follow...ClosedXML - The easy way to OpenXML: ClosedXML 0.65.2: Aside from many bug fixes we now have Conditional Formatting The conditional formatting was sponsored by http://www.bewing.nl (big thanks) New on v0.65.1 Fixed issue when loading conditional formatting with default values for icon sets New on v0.65.2 Fixed issue loading conditional formatting Improved inserts performanceLiberty: v3.2.0.0 Release 4th April 2012: Change Log-Added -Halo 3 support (invincibility, ammo editing) -Halo 3: ODST support (invincibility, ammo editing) -The file transfer page now shows its progress in the Windows 7 taskbar -"About this build" settings page -Reach Change what an object is carrying -Reach Change which node a carried object is attached to -Reach Object node viewer and exporter -Reach Change which weapons you are carrying from the object editor -Reach Edit the weapon controller of vehicles and turrets -An error dia...MSBuild Extension Pack: April 2012: Release Blog Post The MSBuild Extension Pack April 2012 release provides a collection of over 435 MSBuild tasks. A high level summary of what the tasks currently cover includes the following: System Items: Active Directory, Certificates, COM+, Console, Date and Time, Drives, Environment Variables, Event Logs, Files and Folders, FTP, GAC, Network, Performance Counters, Registry, Services, Sound Code: Assemblies, AsyncExec, CAB Files, Code Signing, DynamicExecute, File Detokenisation, GUID’...DotNetNuke® Community Edition CMS: 06.01.05: Major Highlights Fixed issue that stopped users from creating vocabularies when the portal ID was not zero Fixed issue that caused modules configured to be displayed on all pages to be added to the wrong container in new pages Fixed page quota restriction issue in the Ribbon Bar Removed restriction that would not allow users to use a dash in page names. Now users can create pages with names like "site-map" Fixed issue that was causing the wrong container to be loaded in modules wh...51Degrees.mobi - Mobile Device Detection and Redirection: 2.1.3.1: One Click Install from NuGet Changes to Version 2.1.3.11. [assembly: AllowPartiallyTrustedCallers] has been added back into the AssemblyInfo.cs file to prevent failures with other assemblies in Medium trust environments. 2. The Lite data embedded into the assembly has been updated to include devices from December 2011. The 42 new RingMark properties will return Unknown if RingMark data is not available. Changes to Version 2.1.2.11Code Changes 1. The project is now licenced under the Mozilla...MVC Controls Toolkit: Mvc Controls Toolkit 2.0.0: Added Support for Mvc4 beta and WebApi The SafeqQuery and HttpSafeQuery IQueryable implementations that works as wrappers aroung any IQueryable to protect it from unwished queries. "Client Side" pager specialized in paging javascript data coming either from a remote data source, or from local data. LinQ like fluent javascript api to build queries either against remote data sources, or against local javascript data, with exactly the same interface. There are 3 different query objects exp...ExtAspNet: ExtAspNet v3.1.2: ExtAspNet - ?? ExtJS ??? ASP.NET 2.0 ???，????? AJAX ?????????? ExtAspNet ????? ExtJS ??? ASP.NET 2.0 ???，????? AJAX ??????????。 ExtAspNet ??????? JavaScript，?? CSS，?? UpdatePanel，?? ViewState，?? WebServices ???????。 ??????: IE 7.0, Firefox 3.6, Chrome 3.0, Opera 10.5, Safari 3.0+ ????：Apache License 2.0 (Apache) ??：http://extasp.net/ ??：http://bbs.extasp.net/ ??：http://extaspnet.codeplex.com/ ??：http://sanshi.cnblogs.com/ ????： +2012-04-04 v3.1.2 -??IE?????????????BUG（??"about:blank"?...nopCommerce. Open source shopping cart (ASP.NET MVC): nopcommerce 2.50: Highlight features & improvements: • Significant performance optimization. • Allow store owners to create several shipments per order. Added a new shipping status: “Partially shipped”. • Pre-order support added. Enables your customers to place a Pre-Order and pay for the item in advance. Displays “Pre-order” button instead of “Buy Now” on the appropriate pages. Makes it possible for customer to buy available goods and Pre-Order items during one session. It can be managed on a product variant ...WiX Toolset: WiX v3.6 RC0: WiX v3.6 RC0 (3.6.2803.0) provides support for VS11 and a more stable Burn engine. For more information see Rob's blog post about the release: http://robmensching.com/blog/posts/2012/4/3/WiX-v3.6-Release-Candidate-Zero-availableSageFrame: SageFrame 2.0: Sageframe is an open source ASP.NET web development framework developed using ASP.NET 3.5 with service pack 1 (sp1) technology. It is designed specifically to help developers build dynamic website by providing core functionality common to most web applications.iTuner - The iTunes Companion: iTuner 1.5.4475: Fix to parse empty playlists in iTunes LibraryDocument.Editor: 2012.2: Whats New for Document.Editor 2012.2: New Save Copy support New Page Setup support Minor Bug Fix's, improvements and speed upsDotNet.Highcharts: DotNet.Highcharts 1.2 with Examples: Tested and adapted to the latest version of Highcharts 2.2.1 Fixed Issue 359: Not implemented serialization array of type: System.Drawing.Color[] Fixed Issue 364: Crosshairs defined as array of CrosshairsForamt generates bad Highchart code For the example project: Added newest version of Highcharts 2.2.1 Added new demos to How To's section: Bind Data From Dictionary Bind Data From Object List Custom Theme Tooltip Crosshairs Theming The Reset Button Plot Band EventsVidCoder: 1.3.2: Added option for the minimum title length to scan. Added support to enable or disable LibDVDNav. Added option to prompt to delete source files after clearing successful completed items. Added option to disable remembering recent files and folders. Tweaked number box to only select all on a quick click.MJP's DirectX 11 Samples: Light Indexed Deferred Rendering: Implements light indexed deferred using per-tile light lists calculated in a compute shader, as well as a traditional deferred renderer that uses a compute shader for per-tile light culling and per-pixel shading.Pcap.Net: Pcap.Net 0.9.0 (66492): Pcap.Net - March 2012 Release Pcap.Net is a .NET wrapper for WinPcap written in C++/CLI and C#. It Features almost all WinPcap features and includes a packet interpretation framework. Version 0.9.0 (Change Set 66492)March 31, 2012 release of the Pcap.Net framework. Follow Pcap.Net on Google+Follow Pcap.Net on Google+ Files Pcap.Net.DevelopersPack.0.9.0.66492.zip - Includes all the tutorial example projects source files, the binaries in a 3rdParty directory and the documentation. It include...New Projects.Net Mutation Testing Tool: This tool will help for making and unit testing mutation changes. Mutation tests improve unit tests and applications.African Honey Bee Application Suite: This is the home of the software behind the African Honey Bee community enrichment project.Create Schema: Object extension method that generates schema creation scripts in SQL (MS SQL SERVER) from c# classes to rapidly get database tables from an existing class structure. Just edit the scripts (they are just guesses of how the database should look) to make them fit your database needs and then run them as a query in SQL Server. Check out vecklare.blogspot.se for more examples. CrtTfsDemo: demo project to test code review tool integration with tfsDolphins Salaam: This Library is a Cross Platform, UDP Broadcast solution for Peer to Peer network client detection. It is written in pure C# and is Mono and .Net compatible. It has been tested on Mac OS X, Windows, Linux, iOS, Android, Xbox and it is expected to be compatible with every other Mono compatible platform. The library is ready to use out of box and there is almost zero configurations needed for it to start working, regarding that, it is also flexible and configurable for your needs.Enhanced Content Query Webpart: This Enhanced Content Query Webpart for SharePoint 2010 is meant for the advanced application developer. You will be able to create any rollup of pages of any Content Type(s), Site Column(s) from any subsite(s) with (any) style you want. Xslt skills are required.fangxue: huijiaFrameworkComponent: frameworkcomponent 4 companyFsXna3DGame: 3D game written in XNA and F# (still very much a work in progress)GeoLock: GeoLock is a proof of concept (PoC). GeoLock demonstrates how to retrieve geolocation data from surrounding Wi-Fi networks triangulation without Global Positioning System (GPS) hardware. grab-libs: A quick hack to bundle up the shared libraries needed to run an i386 executable on an x86_64 machine.Logical Game Of Life: Make Logic Component with a game of life algoritmMagic Box: Magic Box is the application for "hiding" files in NTFS file system. NTFS Alternate Data Streams are used for this.Notes: Application to create fast notes on your Windows Phone.Orchard Google Infographics: **NOTE: Only works with Orchard >= v1.4** This module leverages Google's Infographics api for generating QR codes for each content item that uses the Orchard.Autoroute part. The api documentation may be found at https://developers.google.com/chart/infographics/docs/qr_codesOutlook Calendar Cleaner: If you port your email from a Lotus Notes server to Exchange Server or to Office 365, your Mac Outlook calendar items may be missing. This includes calendar appointments and meeting requests. This may include items that were ported over and also new items created after the port.Polarity: Polarity is a plugin-oriented bot written in C# for deviantArt chat written with simplicity and ease of use for plugin developers as the number one goal.Pool Game Paradise: Pool Game Club of Augmentum Inc. Wuhan Site.RCT2 DatChecker: A utility for Rollercoaster Tycoon 2 that catalogs, displays, and helps manage object files (*.DAT). Examine objects frame by frame or copy object images to the clipboard. Sort objects by size, type, or content. Use DatChecker to find and remove unwanted or duplicate objects, or RecipeML Manager: This project creates C# classes that support the RecipeML standard. It also enhances that standard to support full daily and weekly menus.s0t0o0c0k3246352543: 345234324324324324ScoutGames: scout games portalSharePoint All Page Scripting: This solution is the skeleton of the JavaScript loading in all pages on the SharePoint site collection. This solution can be deployed as a "sandbox solution". Supports the Office365 of course. ??????????SharePoint ?????????????????????????Java?????????????。 ????????????????????????。 ???、????Office365?????????。testtom04052012git02: testtom04052012git02testtom04052012tfs01: testtom04052012tfs01testtom04052012tfs03: testtom04052012tfs03Visual Studio Pattern Automation Toolkit (VSPAT): VSPAT is a set of development and deployment tools from Microsoft that generate and execute Visual Studio extensions called 'Pattern Toolkits' that redeliver best practices, expertise and proven solutions faster, more reliably and more consistently. If you are an *IT professional* are you are looking to build and deploy custom solutions that include proven best practices to improve quality, consistency and time to market. And if you wish to spend significantly less time having to learn all...Wet: Wet, the game.WPF Data Editors: WPF Data Editor controls contains most of editor controls in WPF.xSolon Instructions: Framework to run scripts

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• C#/.NET Little Wonders: The Useful But Overlooked Sets

  - by James Michael Hare

  Once again we consider some of the lesser known classes and keywords of C#.  Today we will be looking at two set implementations in the System.Collections.Generic namespace: HashSet<T> and SortedSet<T>.  Even though most people think of sets as mathematical constructs, they are actually very useful classes that can be used to help make your application more performant if used appropriately. A Background From Math In mathematical terms, a set is an unordered collection of unique items.  In other words, the set {2,3,5} is identical to the set {3,5,2}.  In addition, the set {2, 2, 4, 1} would be invalid because it would have a duplicate item (2).  In addition, you can perform set arithmetic on sets such as: Intersections: The intersection of two sets is the collection of elements common to both.  Example: The intersection of {1,2,5} and {2,4,9} is the set {2}. Unions: The union of two sets is the collection of unique items present in either or both set.  Example: The union of {1,2,5} and {2,4,9} is {1,2,4,5,9}. Differences: The difference of two sets is the removal of all items from the first set that are common between the sets.  Example: The difference of {1,2,5} and {2,4,9} is {1,5}. Supersets: One set is a superset of a second set if it contains all elements that are in the second set. Example: The set {1,2,5} is a superset of {1,5}. Subsets: One set is a subset of a second set if all the elements of that set are contained in the first set. Example: The set {1,5} is a subset of {1,2,5}. If We’re Not Doing Math, Why Do We Care? Now, you may be thinking: why bother with the set classes in C# if you have no need for mathematical set manipulation?  The answer is simple: they are extremely efficient ways to determine ownership in a collection. For example, let’s say you are designing an order system that tracks the price of a particular equity, and once it reaches a certain point will trigger an order.  Now, since there’s tens of thousands of equities on the markets, you don’t want to track market data for every ticker as that would be a waste of time and processing power for symbols you don’t have orders for.  Thus, we just want to subscribe to the stock symbol for an equity order only if it is a symbol we are not already subscribed to. Every time a new order comes in, we will check the list of subscriptions to see if the new order’s stock symbol is in that list.  If it is, great, we already have that market data feed!  If not, then and only then should we subscribe to the feed for that symbol. So far so good, we have a collection of symbols and we want to see if a symbol is present in that collection and if not, add it.  This really is the essence of set processing, but for the sake of comparison, let’s say you do a list instead: 1: // class that handles are order processing service 2: public sealed class OrderProcessor 3: { 4: // contains list of all symbols we are currently subscribed to 5: private readonly List<string> _subscriptions = new List<string>(); 6:  7: ... 8: } Now whenever you are adding a new order, it would look something like: 1: public PlaceOrderResponse PlaceOrder(Order newOrder) 2: { 3: // do some validation, of course... 4:  5: // check to see if already subscribed, if not add a subscription 6: if (!_subscriptions.Contains(newOrder.Symbol)) 7: { 8: // add the symbol to the list 9: _subscriptions.Add(newOrder.Symbol); 10: 11: // do whatever magic is needed to start a subscription for the symbol 12: } 13:  14: // place the order logic! 15: } What’s wrong with this?  In short: performance!  Finding an item inside a List<T> is a linear - O(n) – operation, which is not a very performant way to find if an item exists in a collection. (I used to teach algorithms and data structures in my spare time at a local university, and when you began talking about big-O notation you could immediately begin to see eyes glossing over as if it was pure, useless theory that would not apply in the real world, but I did and still do believe it is something worth understanding well to make the best choices in computer science). Let’s think about this: a linear operation means that as the number of items increases, the time that it takes to perform the operation tends to increase in a linear fashion.  Put crudely, this means if you double the collection size, you might expect the operation to take something like the order of twice as long.  Linear operations tend to be bad for performance because they mean that to perform some operation on a collection, you must potentially “visit” every item in the collection.  Consider finding an item in a List<T>: if you want to see if the list has an item, you must potentially check every item in the list before you find it or determine it’s not found. Now, we could of course sort our list and then perform a binary search on it, but sorting is typically a linear-logarithmic complexity – O(n * log n) - and could involve temporary storage.  So performing a sort after each add would probably add more time.  As an alternative, we could use a SortedList<TKey, TValue> which sorts the list on every Add(), but this has a similar level of complexity to move the items and also requires a key and value, and in our case the key is the value. This is why sets tend to be the best choice for this type of processing: they don’t rely on separate keys and values for ordering – so they save space – and they typically don’t care about ordering – so they tend to be extremely performant.  The .NET BCL (Base Class Library) has had the HashSet<T> since .NET 3.5, but at that time it did not implement the ISet<T> interface.  As of .NET 4.0, HashSet<T> implements ISet<T> and a new set, the SortedSet<T> was added that gives you a set with ordering. HashSet<T> – For Unordered Storage of Sets When used right, HashSet<T> is a beautiful collection, you can think of it as a simplified Dictionary<T,T>.  That is, a Dictionary where the TKey and TValue refer to the same object.  This is really an oversimplification, but logically it makes sense.  I’ve actually seen people code a Dictionary<T,T> where they store the same thing in the key and the value, and that’s just inefficient because of the extra storage to hold both the key and the value. As it’s name implies, the HashSet<T> uses a hashing algorithm to find the items in the set, which means it does take up some additional space, but it has lightning fast lookups!  Compare the times below between HashSet<T> and List<T>: Operation HashSet<T> List<T> Add() O(1) O(1) at end O(n) in middle Remove() O(1) O(n) Contains() O(1) O(n)   Now, these times are amortized and represent the typical case.  In the very worst case, the operations could be linear if they involve a resizing of the collection – but this is true for both the List and HashSet so that’s a less of an issue when comparing the two. The key thing to note is that in the general case, HashSet is constant time for adds, removes, and contains!  This means that no matter how large the collection is, it takes roughly the exact same amount of time to find an item or determine if it’s not in the collection.  Compare this to the List where almost any add or remove must rearrange potentially all the elements!  And to find an item in the list (if unsorted) you must search every item in the List. So as you can see, if you want to create an unordered collection and have very fast lookup and manipulation, the HashSet is a great collection. And since HashSet<T> implements ICollection<T> and IEnumerable<T>, it supports nearly all the same basic operations as the List<T> and can use the System.Linq extension methods as well. All we have to do to switch from a List<T> to a HashSet<T>  is change our declaration.  Since List and HashSet support many of the same members, chances are we won’t need to change much else. 1: public sealed class OrderProcessor 2: { 3: private readonly HashSet<string> _subscriptions = new HashSet<string>(); 4:  5: // ... 6:  7: public PlaceOrderResponse PlaceOrder(Order newOrder) 8: { 9: // do some validation, of course... 10: 11: // check to see if already subscribed, if not add a subscription 12: if (!_subscriptions.Contains(newOrder.Symbol)) 13: { 14: // add the symbol to the list 15: _subscriptions.Add(newOrder.Symbol); 16: 17: // do whatever magic is needed to start a subscription for the symbol 18: } 19: 20: // place the order logic! 21: } 22:  23: // ... 24: } 25: Notice, we didn’t change any code other than the declaration for _subscriptions to be a HashSet<T>.  Thus, we can pick up the performance improvements in this case with minimal code changes. SortedSet<T> – Ordered Storage of Sets Just like HashSet<T> is logically similar to Dictionary<T,T>, the SortedSet<T> is logically similar to the SortedDictionary<T,T>. The SortedSet can be used when you want to do set operations on a collection, but you want to maintain that collection in sorted order.  Now, this is not necessarily mathematically relevant, but if your collection needs do include order, this is the set to use. So the SortedSet seems to be implemented as a binary tree (possibly a red-black tree) internally.  Since binary trees are dynamic structures and non-contiguous (unlike List and SortedList) this means that inserts and deletes do not involve rearranging elements, or changing the linking of the nodes.  There is some overhead in keeping the nodes in order, but it is much smaller than a contiguous storage collection like a List<T>.  Let’s compare the three: Operation HashSet<T> SortedSet<T> List<T> Add() O(1) O(log n) O(1) at end O(n) in middle Remove() O(1) O(log n) O(n) Contains() O(1) O(log n) O(n)   The MSDN documentation seems to indicate that operations on SortedSet are O(1), but this seems to be inconsistent with its implementation and seems to be a documentation error.  There’s actually a separate MSDN document (here) on SortedSet that indicates that it is, in fact, logarithmic in complexity.  Let’s put it in layman’s terms: logarithmic means you can double the collection size and typically you only add a single extra “visit” to an item in the collection.  Take that in contrast to List<T>’s linear operation where if you double the size of the collection you double the “visits” to items in the collection.  This is very good performance!  It’s still not as performant as HashSet<T> where it always just visits one item (amortized), but for the addition of sorting this is a good thing. Consider the following table, now this is just illustrative data of the relative complexities, but it’s enough to get the point: Collection Size O(1) Visits O(log n) Visits O(n) Visits 1 1 1 1 10 1 4 10 100 1 7 100 1000 1 10 1000   Notice that the logarithmic – O(log n) – visit count goes up very slowly compare to the linear – O(n) – visit count.  This is because since the list is sorted, it can do one check in the middle of the list, determine which half of the collection the data is in, and discard the other half (binary search).  So, if you need your set to be sorted, you can use the SortedSet<T> just like the HashSet<T> and gain sorting for a small performance hit, but it’s still faster than a List<T>. Unique Set Operations Now, if you do want to perform more set-like operations, both implementations of ISet<T> support the following, which play back towards the mathematical set operations described before: IntersectWith() – Performs the set intersection of two sets.  Modifies the current set so that it only contains elements also in the second set. UnionWith() – Performs a set union of two sets.  Modifies the current set so it contains all elements present both in the current set and the second set. ExceptWith() – Performs a set difference of two sets.  Modifies the current set so that it removes all elements present in the second set. IsSupersetOf() – Checks if the current set is a superset of the second set. IsSubsetOf() – Checks if the current set is a subset of the second set. For more information on the set operations themselves, see the MSDN description of ISet<T> (here). What Sets Don’t Do Don’t get me wrong, sets are not silver bullets.  You don’t really want to use a set when you want separate key to value lookups, that’s what the IDictionary implementations are best for. Also sets don’t store temporal add-order.  That is, if you are adding items to the end of a list all the time, your list is ordered in terms of when items were added to it.  This is something the sets don’t do naturally (though you could use a SortedSet with an IComparer with a DateTime but that’s overkill) but List<T> can. Also, List<T> allows indexing which is a blazingly fast way to iterate through items in the collection.  Iterating over all the items in a List<T> is generally much, much faster than iterating over a set. Summary Sets are an excellent tool for maintaining a lookup table where the item is both the key and the value.  In addition, if you have need for the mathematical set operations, the C# sets support those as well.  The HashSet<T> is the set of choice if you want the fastest possible lookups but don’t care about order.  In contrast the SortedSet<T> will give you a sorted collection at a slight reduction in performance.   Technorati Tags: C#,.Net,Little Wonders,BlackRabbitCoder,ISet,HashSet,SortedSet

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• Connecting SceneBuilder edited FXML to Java code

  - by daniel

  Recently I had to answer several questions regarding how to connect an UI built with the JavaFX SceneBuilder 1.0 Developer Preview to Java Code. So I figured out that a short overview might be helpful. But first, let me state the obvious. What is FXML? To make it short, FXML is an XML based declaration format for JavaFX. JavaFX provides an FXML loader which will parse FXML files and from that construct a graph of Java object. It may sound complex when stated like that but it is actually quite simple. Here is an example of FXML file, which instantiate a StackPane and puts a Button inside it: -- <?xml version="1.0" encoding="UTF-8"?> <?import java.lang.*?> <?import java.util.*?> <?import javafx.scene.control.*?> <?import javafx.scene.layout.*?> <?import javafx.scene.paint.*?> <StackPane prefHeight="150.0" prefWidth="200.0" xmlns:fx="http://javafx.com/fxml"> <children> <Button mnemonicParsing="false" text="Button" /> </children> </StackPane> ... and here is the code I would have had to write if I had chosen to do the same thing programatically: import javafx.scene.control.*; import javafx.scene.layout.*; ... final Button button = new Button("Button"); button.setMnemonicParsing(false); final StackPane stackPane = new StackPane(); stackPane.setPrefWidth(200.0); stackPane.setPrefHeight(150.0); stacPane.getChildren().add(button); As you can see - FXML is rather simple to understand - as it is quite close to the JavaFX API. So OK FXML is simple, but why would I use it?Well, there are several answers to that - but my own favorite is: because you can make it with SceneBuilder. What is SceneBuilder? In short SceneBuilder is a layout tool that will let you graphically build JavaFX user interfaces by dragging and dropping JavaFX components from a library, and save it as an FXML file. SceneBuilder can also be used to load and modify JavaFX scenegraphs declared in FXML. Here is how I made the small FXML file above: Start the JavaFX SceneBuilder 1.0 Developer Preview In the Library on the left hand side, click on 'StackPane' and drag it on the content view (the white rectangle) In the Library, select a Button and drag it onto the StackPane on the content view. In the Hierarchy Panel on the left hand side - select the StackPane component, then invoke 'Edit > Trim To Selected' from the menubar That's it - you can now save, and you will obtain the small FXML file shown above. Of course this is only a trivial sample, made for the sake of the example - and SceneBuilder will let you create much more complex UIs. So, I have now an FXML file. But what do I do with it? How do I include it in my program? How do I write my main class? Loading an FXML file with JavaFX Well, that's the easy part - because the piece of code you need to write never changes. You can download and look at the SceneBuilder samples if you need to get convinced, but here is the short version: Create a Java class (let's call it 'Main.java') which extends javafx.application.Application In the same directory copy/save the FXML file you just created using SceneBuilder. Let's name it "simple.fxml" Now here is the Java code for the Main class, which simply loads the FXML file and puts it as root in a stage's scene. /* * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved. */ package simple; import java.util.logging.Level; import java.util.logging.Logger; import javafx.application.Application; import javafx.fxml.FXMLLoader; import javafx.scene.Scene; import javafx.scene.layout.StackPane; import javafx.stage.Stage; public class Main extends Application { /** * @param args the command line arguments */ public static void main(String[] args) { Application.launch(Main.class, (java.lang.String[])null); } @Override public void start(Stage primaryStage) { try { StackPane page = (StackPane) FXMLLoader.load(Main.class.getResource("simple.fxml")); Scene scene = new Scene(page); primaryStage.setScene(scene); primaryStage.setTitle("FXML is Simple"); primaryStage.show(); } catch (Exception ex) { Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex); } } } Great! Now I only have to use my favorite IDE to compile the class and run it. But... wait... what does it do? Well nothing. It just displays a button in the middle of a window. There's no logic attached to it. So how do we do that? How can I connect this button to my application logic? Here is how: Connection to code First let's define our application logic. Since this post is only intended to give a very brief overview - let's keep things simple. Let's say that the only thing I want to do is print a message on System.out when the user clicks on my button. To do that, I'll need to register an action handler with my button. And to do that, I'll need to somehow get a handle on my button. I'll need some kind of controller logic that will get my button and add my action handler to it. So how do I get a handle to my button and pass it to my controller? Once again - this is easy: I just need to write a controller class for my FXML. With each FXML file, it is possible to associate a controller class defined for that FXML. That controller class will make the link between the UI (the objects defined in the FXML) and the application logic. To each object defined in FXML we can associate an fx:id. The value of the id must be unique within the scope of the FXML, and is the name of an instance variable inside the controller class, in which the object will be injected. Since I want to have access to my button, I will need to add an fx:id to my button in FXML, and declare an @FXML variable in my controller class with the same name. In other words - I will need to add fx:id="myButton" to my button in FXML: -- <Button fx:id="myButton" mnemonicParsing="false" text="Button" /> and declare @FXML private Button myButton in my controller class @FXML private Button myButton; // value will be injected by the FXMLLoader Let's see how to do this. Add an fx:id to the Button object Load "simple.fxml" in SceneBuilder - if not already done In the hierarchy panel (bottom left), or directly on the content view, select the Button object. Open the Properties sections of the inspector (right panel) for the button object At the top of the section, you will see a text field labelled fx:id. Enter myButton in that field and validate. Associate a controller class with the FXML file Still in SceneBuilder, select the top root object (in our case, that's the StackPane), and open the Code section of the inspector (right hand side) At the top of the section you should see a text field labelled Controller Class. In the field, type simple.SimpleController. This is the name of the class we're going to create manually. If you save at this point, the FXML will look like this: -- <?xml version="1.0" encoding="UTF-8"?> <?import java.lang.*?> <?import java.util.*?> <?import javafx.scene.control.*?> <?import javafx.scene.layout.*?> <?import javafx.scene.paint.*?> <StackPane prefHeight="150.0" prefWidth="200.0" xmlns:fx="http://javafx.com/fxml" fx:controller="simple.SimpleController"> <children> <Button fx:id="myButton" mnemonicParsing="false" text="Button" /> </children> </StackPane> As you can see, the name of the controller class has been added to the root object: fx:controller="simple.SimpleController" Coding the controller class In your favorite IDE, create an empty SimpleController.java class. Now what does a controller class looks like? What should we put inside? Well - SceneBuilder will help you there: it will show you an example of controller skeleton tailored for your FXML. In the menu bar, invoke View > Show Sample Controller Skeleton. A popup appears, displaying a suggestion for the controller skeleton: copy the code displayed there, and paste it into your SimpleController.java: /** * Sample Skeleton for "simple.fxml" Controller Class * Use copy/paste to copy paste this code into your favorite IDE **/ package simple; import java.net.URL; import java.util.ResourceBundle; import javafx.fxml.FXML; import javafx.fxml.Initializable; import javafx.scene.control.Button; public class SimpleController implements Initializable { @FXML // fx:id="myButton" private Button myButton; // Value injected by FXMLLoader @Override // This method is called by the FXMLLoader when initialization is complete public void initialize(URL fxmlFileLocation, ResourceBundle resources) { assert myButton != null : "fx:id=\"myButton\" was not injected: check your FXML file 'simple.fxml'."; // initialize your logic here: all @FXML variables will have been injected } } Note that the code displayed by SceneBuilder is there only for educational purpose: SceneBuilder does not create and does not modify Java files. This is simply a hint of what you can use, given the fx:id present in your FXML file. You are free to copy all or part of the displayed code and paste it into your own Java class. Now at this point, there only remains to add our logic to the controller class. Quite easy: in the initialize method, I will register an action handler with my button: () { @Override public void handle(ActionEvent event) { System.out.println("That was easy, wasn't it?"); } }); ... -- ... // initialize your logic here: all @FXML variables will have been injected myButton.setOnAction(new EventHandler<ActionEvent>() { @Override public void handle(ActionEvent event) { System.out.println("That was easy, wasn't it?"); } }); ... That's it - if you now compile everything in your IDE, and run your application, clicking on the button should print a message on the console! Summary What happens is that in Main.java, the FXMLLoader will load simple.fxml from the jar/classpath, as specified by 'FXMLLoader.load(Main.class.getResource("simple.fxml"))'. When loading simple.fxml, the loader will find the name of the controller class, as specified by 'fx:controller="simple.SimpleController"' in the FXML. Upon finding the name of the controller class, the loader will create an instance of that class, in which it will try to inject all the objects that have an fx:id in the FXML. Thus, after having created '<Button fx:id="myButton" ... />', the FXMLLoader will inject the button instance into the '@FXML private Button myButton;' instance variable found on the controller instance. This is because The instance variable has an @FXML annotation, The name of the variable exactly matches the value of the fx:id Finally, when the whole FXML has been loaded, the FXMLLoader will call the controller's initialize method, and our code that registers an action handler with the button will be executed. For a complete example, take a look at the HelloWorld SceneBuilder sample. Also make sure to follow the SceneBuilder Get Started guide, which will guide you through a much more complete example. Of course, there are more elegant ways to set up an Event Handler using FXML and SceneBuilder. There are also many different ways to work with the FXMLLoader. But since it's starting to be very late here, I think it will have to wait for another post. I hope you have enjoyed the tour! --daniel

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• The Incremental Architect&rsquo;s Napkin - #5 - Design functions for extensibility and readability

  - by Ralf Westphal

  Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/08/24/the-incremental-architectrsquos-napkin---5---design-functions-for.aspx The functionality of programs is entered via Entry Points. So what we´re talking about when designing software is a bunch of functions handling the requests represented by and flowing in through those Entry Points. Designing software thus consists of at least three phases: Analyzing the requirements to find the Entry Points and their signatures Designing the functionality to be executed when those Entry Points get triggered Implementing the functionality according to the design aka coding I presume, you´re familiar with phase 1 in some way. And I guess you´re proficient in implementing functionality in some programming language. But in my experience developers in general are not experienced in going through an explicit phase 2. “Designing functionality? What´s that supposed to mean?” you might already have thought. Here´s my definition: To design functionality (or functional design for short) means thinking about… well, functions. You find a solution for what´s supposed to happen when an Entry Point gets triggered in terms of functions. A conceptual solution that is, because those functions only exist in your head (or on paper) during this phase. But you may have guess that, because it´s “design” not “coding”. And here is, what functional design is not: It´s not about logic. Logic is expressions (e.g. +, -, && etc.) and control statements (e.g. if, switch, for, while etc.). Also I consider calling external APIs as logic. It´s equally basic. It´s what code needs to do in order to deliver some functionality or quality. Logic is what´s doing that needs to be done by software. Transformations are either done through expressions or API-calls. And then there is alternative control flow depending on the result of some expression. Basically it´s just jumps in Assembler, sometimes to go forward (if, switch), sometimes to go backward (for, while, do). But calling your own function is not logic. It´s not necessary to produce any outcome. Functionality is not enhanced by adding functions (subroutine calls) to your code. Nor is quality increased by adding functions. No performance gain, no higher scalability etc. through functions. Functions are not relevant to functionality. Strange, isn´t it. What they are important for is security of investment. By introducing functions into our code we can become more productive (re-use) and can increase evolvability (higher unterstandability, easier to keep code consistent). That´s no small feat, however. Evolvable code can hardly be overestimated. That´s why to me functional design is so important. It´s at the core of software development. To sum this up: Functional design is on a level of abstraction above (!) logical design or algorithmic design. Functional design is only done until you get to a point where each function is so simple you are very confident you can easily code it. Functional design an logical design (which mostly is coding, but can also be done using pseudo code or flow charts) are complementary. Software needs both. If you start coding right away you end up in a tangled mess very quickly. Then you need back out through refactoring. Functional design on the other hand is bloodless without actual code. It´s just a theory with no experiments to prove it. But how to do functional design? An example of functional design Let´s assume a program to de-duplicate strings. The user enters a number of strings separated by commas, e.g. a, b, a, c, d, b, e, c, a. And the program is supposed to clear this list of all doubles, e.g. a, b, c, d, e. There is only one Entry Point to this program: the user triggers the de-duplication by starting the program with the string list on the command line C:\>deduplicate "a, b, a, c, d, b, e, c, a" a, b, c, d, e …or by clicking on a GUI button. This leads to the Entry Point function to get called. It´s the program´s main function in case of the batch version or a button click event handler in the GUI version. That´s the physical Entry Point so to speak. It´s inevitable. What then happens is a three step process: Transform the input data from the user into a request. Call the request handler. Transform the output of the request handler into a tangible result for the user. Or to phrase it a bit more generally: Accept input. Transform input into output. Present output. This does not mean any of these steps requires a lot of effort. Maybe it´s just one line of code to accomplish it. Nevertheless it´s a distinct step in doing the processing behind an Entry Point. Call it an aspect or a responsibility - and you will realize it most likely deserves a function of its own to satisfy the Single Responsibility Principle (SRP). Interestingly the above list of steps is already functional design. There is no logic, but nevertheless the solution is described - albeit on a higher level of abstraction than you might have done yourself. But it´s still on a meta-level. The application to the domain at hand is easy, though: Accept string list from command line De-duplicate Present de-duplicated strings on standard output And this concrete list of processing steps can easily be transformed into code:static void Main(string[] args) { var input = Accept_string_list(args); var output = Deduplicate(input); Present_deduplicated_string_list(output); } Instead of a big problem there are three much smaller problems now. If you think each of those is trivial to implement, then go for it. You can stop the functional design at this point. But maybe, just maybe, you´re not so sure how to go about with the de-duplication for example. Then just implement what´s easy right now, e.g.private static string Accept_string_list(string[] args) { return args[0]; } private static void Present_deduplicated_string_list( string[] output) { var line = string.Join(", ", output); Console.WriteLine(line); } Accept_string_list() contains logic in the form of an API-call. Present_deduplicated_string_list() contains logic in the form of an expression and an API-call. And then repeat the functional design for the remaining processing step. What´s left is the domain logic: de-duplicating a list of strings. How should that be done? Without any logic at our disposal during functional design you´re left with just functions. So which functions could make up the de-duplication? Here´s a suggestion: De-duplicate Parse the input string into a true list of strings. Register each string in a dictionary/map/set. That way duplicates get cast away. Transform the data structure into a list of unique strings. Processing step 2 obviously was the core of the solution. That´s where real creativity was needed. That´s the core of the domain. But now after this refinement the implementation of each step is easy again:private static string[] Parse_string_list(string input) { return input.Split(',') .Select(s => s.Trim()) .ToArray(); } private static Dictionary<string,object> Compile_unique_strings(string[] strings) { return strings.Aggregate( new Dictionary<string, object>(), (agg, s) => { agg[s] = null; return agg; }); } private static string[] Serialize_unique_strings( Dictionary<string,object> dict) { return dict.Keys.ToArray(); } With these three additional functions Main() now looks like this:static void Main(string[] args) { var input = Accept_string_list(args); var strings = Parse_string_list(input); var dict = Compile_unique_strings(strings); var output = Serialize_unique_strings(dict); Present_deduplicated_string_list(output); } I think that´s very understandable code: just read it from top to bottom and you know how the solution to the problem works. It´s a mirror image of the initial design: Accept string list from command line Parse the input string into a true list of strings. Register each string in a dictionary/map/set. That way duplicates get cast away. Transform the data structure into a list of unique strings. Present de-duplicated strings on standard output You can even re-generate the design by just looking at the code. Code and functional design thus are always in sync - if you follow some simple rules. But about that later. And as a bonus: all the functions making up the process are small - which means easy to understand, too. So much for an initial concrete example. Now it´s time for some theory. Because there is method to this madness ;-) The above has only scratched the surface. Introducing Flow Design Functional design starts with a given function, the Entry Point. Its goal is to describe the behavior of the program when the Entry Point is triggered using a process, not an algorithm. An algorithm consists of logic, a process on the other hand consists just of steps or stages. Each processing step transforms input into output or a side effect. Also it might access resources, e.g. a printer, a database, or just memory. Processing steps thus can rely on state of some sort. This is different from Functional Programming, where functions are supposed to not be stateful and not cause side effects.[1] In its simplest form a process can be written as a bullet point list of steps, e.g. Get data from user Output result to user Transform data Parse data Map result for output Such a compilation of steps - possibly on different levels of abstraction - often is the first artifact of functional design. It can be generated by a team in an initial design brainstorming. Next comes ordering the steps. What should happen first, what next etc.? Get data from user Parse data Transform data Map result for output Output result to user That´s great for a start into functional design. It´s better than starting to code right away on a given function using TDD. Please get me right: TDD is a valuable practice. But it can be unnecessarily hard if the scope of a functionn is too large. But how do you know beforehand without investing some thinking? And how to do this thinking in a systematic fashion? My recommendation: For any given function you´re supposed to implement first do a functional design. Then, once you´re confident you know the processing steps - which are pretty small - refine and code them using TDD. You´ll see that´s much, much easier - and leads to cleaner code right away. For more information on this approach I call “Informed TDD” read my book of the same title. Thinking before coding is smart. And writing down the solution as a bunch of functions possibly is the simplest thing you can do, I´d say. It´s more according to the KISS (Keep It Simple, Stupid) principle than returning constants or other trivial stuff TDD development often is started with. So far so good. A simple ordered list of processing steps will do to start with functional design. As shown in the above example such steps can easily be translated into functions. Moving from design to coding thus is simple. However, such a list does not scale. Processing is not always that simple to be captured in a list. And then the list is just text. Again. Like code. That means the design is lacking visuality. Textual representations need more parsing by your brain than visual representations. Plus they are limited in their “dimensionality”: text just has one dimension, it´s sequential. Alternatives and parallelism are hard to encode in text. In addition the functional design using numbered lists lacks data. It´s not visible what´s the input, output, and state of the processing steps. That´s why functional design should be done using a lightweight visual notation. No tool is necessary to draw such designs. Use pen and paper; a flipchart, a whiteboard, or even a napkin is sufficient. Visualizing processes The building block of the functional design notation is a functional unit. I mostly draw it like this: Something is done, it´s clear what goes in, it´s clear what comes out, and it´s clear what the processing step requires in terms of state or hardware. Whenever input flows into a functional unit it gets processed and output is produced and/or a side effect occurs. Flowing data is the driver of something happening. That´s why I call this approach to functional design Flow Design. It´s about data flow instead of control flow. Control flow like in algorithms is of no concern to functional design. Thinking about control flow simply is too low level. Once you start with control flow you easily get bogged down by tons of details. That´s what you want to avoid during design. Design is supposed to be quick, broad brush, abstract. It should give overview. But what about all the details? As Robert C. Martin rightly said: “Programming is abot detail”. Detail is a matter of code. Once you start coding the processing steps you designed you can worry about all the detail you want. Functional design does not eliminate all the nitty gritty. It just postpones tackling them. To me that´s also an example of the SRP. Function design has the responsibility to come up with a solution to a problem posed by a single function (Entry Point). And later coding has the responsibility to implement the solution down to the last detail (i.e. statement, API-call). TDD unfortunately mixes both responsibilities. It´s just coding - and thereby trying to find detailed implementations (green phase) plus getting the design right (refactoring). To me that´s one reason why TDD has failed to deliver on its promise for many developers. Using functional units as building blocks of functional design processes can be depicted very easily. Here´s the initial process for the example problem: For each processing step draw a functional unit and label it. Choose a verb or an “action phrase” as a label, not a noun. Functional design is about activities, not state or structure. Then make the output of an upstream step the input of a downstream step. Finally think about the data that should flow between the functional units. Write the data above the arrows connecting the functional units in the direction of the data flow. Enclose the data description in brackets. That way you can clearly see if all flows have already been specified. Empty brackets mean “no data is flowing”, but nevertheless a signal is sent. A name like “list” or “strings” in brackets describes the data content. Use lower case labels for that purpose. A name starting with an upper case letter like “String” or “Customer” on the other hand signifies a data type. If you like, you also can combine descriptions with data types by separating them with a colon, e.g. (list:string) or (strings:string[]). But these are just suggestions from my practice with Flow Design. You can do it differently, if you like. Just be sure to be consistent. Flows wired-up in this manner I call one-dimensional (1D). Each functional unit just has one input and/or one output. A functional unit without an output is possible. It´s like a black hole sucking up input without producing any output. Instead it produces side effects. A functional unit without an input, though, does make much sense. When should it start to work? What´s the trigger? That´s why in the above process even the first processing step has an input. If you like, view such 1D-flows as pipelines. Data is flowing through them from left to right. But as you can see, it´s not always the same data. It get´s transformed along its passage: (args) becomes a (list) which is turned into (strings). The Principle of Mutual Oblivion A very characteristic trait of flows put together from function units is: no functional units knows another one. They are all completely independent of each other. Functional units don´t know where their input is coming from (or even when it´s gonna arrive). They just specify a range of values they can process. And they promise a certain behavior upon input arriving. Also they don´t know where their output is going. They just produce it in their own time independent of other functional units. That means at least conceptually all functional units work in parallel. Functional units don´t know their “deployment context”. They now nothing about the overall flow they are place in. They are just consuming input from some upstream, and producing output for some downstream. That makes functional units very easy to test. At least as long as they don´t depend on state or resources. I call this the Principle of Mutual Oblivion (PoMO). Functional units are oblivious of others as well as an overall context/purpose. They are just parts of a whole focused on a single responsibility. How the whole is built, how a larger goal is achieved, is of no concern to the single functional units. By building software in such a manner, functional design interestingly follows nature. Nature´s building blocks for organisms also follow the PoMO. The cells forming your body do not know each other. Take a nerve cell “controlling” a muscle cell for example:[2] The nerve cell does not know anything about muscle cells, let alone the specific muscel cell it is “attached to”. Likewise the muscle cell does not know anything about nerve cells, let a lone a specific nerve cell “attached to” it. Saying “the nerve cell is controlling the muscle cell” thus only makes sense when viewing both from the outside. “Control” is a concept of the whole, not of its parts. Control is created by wiring-up parts in a certain way. Both cells are mutually oblivious. Both just follow a contract. One produces Acetylcholine (ACh) as output, the other consumes ACh as input. Where the ACh is going, where it´s coming from neither cell cares about. Million years of evolution have led to this kind of division of labor. And million years of evolution have produced organism designs (DNA) which lead to the production of these different cell types (and many others) and also to their co-location. The result: the overall behavior of an organism. How and why this happened in nature is a mystery. For our software, though, it´s clear: functional and quality requirements needs to be fulfilled. So we as developers have to become “intelligent designers” of “software cells” which we put together to form a “software organism” which responds in satisfying ways to triggers from it´s environment. My bet is: If nature gets complex organisms working by following the PoMO, who are we to not apply this recipe for success to our much simpler “machines”? So my rule is: Wherever there is functionality to be delivered, because there is a clear Entry Point into software, design the functionality like nature would do it. Build it from mutually oblivious functional units. That´s what Flow Design is about. In that way it´s even universal, I´d say. Its notation can also be applied to biology: Never mind labeling the functional units with nouns. That´s ok in Flow Design. You´ll do that occassionally for functional units on a higher level of abstraction or when their purpose is close to hardware. Getting a cockroach to roam your bedroom takes 1,000,000 nerve cells (neurons). Getting the de-duplication program to do its job just takes 5 “software cells” (functional units). Both, though, follow the same basic principle. Translating functional units into code Moving from functional design to code is no rocket science. In fact it´s straightforward. There are two simple rules: Translate an input port to a function. Translate an output port either to a return statement in that function or to a function pointer visible to that function. The simplest translation of a functional unit is a function. That´s what you saw in the above example. Functions are mutually oblivious. That why Functional Programming likes them so much. It makes them composable. Which is the reason, nature works according to the PoMO. Let´s be clear about one thing: There is no dependency injection in nature. For all of an organism´s complexity no DI container is used. Behavior is the result of smooth cooperation between mutually oblivious building blocks. Functions will often be the adequate translation for the functional units in your designs. But not always. Take for example the case, where a processing step should not always produce an output. Maybe the purpose is to filter input. Here the functional unit consumes words and produces words. But it does not pass along every word flowing in. Some words are swallowed. Think of a spell checker. It probably should not check acronyms for correctness. There are too many of them. Or words with no more than two letters. Such words are called “stop words”. In the above picture the optionality of the output is signified by the astrisk outside the brackets. It means: Any number of (word) data items can flow from the functional unit for each input data item. It might be none or one or even more. This I call a stream of data. Such behavior cannot be translated into a function where output is generated with return. Because a function always needs to return a value. So the output port is translated into a function pointer or continuation which gets passed to the subroutine when called:[3]void filter_stop_words( string word, Action<string> onNoStopWord) { if (...check if not a stop word...) onNoStopWord(word); } If you want to be nitpicky you might call such a function pointer parameter an injection. And technically you´re right. Conceptually, though, it´s not an injection. Because the subroutine is not functionally dependent on the continuation. Firstly continuations are procedures, i.e. subroutines without a return type. Remember: Flow Design is about unidirectional data flow. Secondly the name of the formal parameter is chosen in a way as to not assume anything about downstream processing steps. onNoStopWord describes a situation (or event) within the functional unit only. Translating output ports into function pointers helps keeping functional units mutually oblivious in cases where output is optional or produced asynchronically. Either pass the function pointer to the function upon call. Or make it global by putting it on the encompassing class. Then it´s called an event. In C# that´s even an explicit feature.class Filter { public void filter_stop_words( string word) { if (...check if not a stop word...) onNoStopWord(word); } public event Action<string> onNoStopWord; } When to use a continuation and when to use an event dependens on how a functional unit is used in flows and how it´s packed together with others into classes. You´ll see examples further down the Flow Design road. Another example of 1D functional design Let´s see Flow Design once more in action using the visual notation. How about the famous word wrap kata? Robert C. Martin has posted a much cited solution including an extensive reasoning behind his TDD approach. So maybe you want to compare it to Flow Design. The function signature given is:string WordWrap(string text, int maxLineLength) {...} That´s not an Entry Point since we don´t see an application with an environment and users. Nevertheless it´s a function which is supposed to provide a certain functionality. The text passed in has to be reformatted. The input is a single line of arbitrary length consisting of words separated by spaces. The output should consist of one or more lines of a maximum length specified. If a word is longer than a the maximum line length it can be split in multiple parts each fitting in a line. Flow Design Let´s start by brainstorming the process to accomplish the feat of reformatting the text. What´s needed? Words need to be assembled into lines Words need to be extracted from the input text The resulting lines need to be assembled into the output text Words too long to fit in a line need to be split Does sound about right? I guess so. And it shows a kind of priority. Long words are a special case. So maybe there is a hint for an incremental design here. First let´s tackle “average words” (words not longer than a line). Here´s the Flow Design for this increment: The the first three bullet points turned into functional units with explicit data added. As the signature requires a text is transformed into another text. See the input of the first functional unit and the output of the last functional unit. In between no text flows, but words and lines. That´s good to see because thereby the domain is clearly represented in the design. The requirements are talking about words and lines and here they are. But note the asterisk! It´s not outside the brackets but inside. That means it´s not a stream of words or lines, but lists or sequences. For each text a sequence of words is output. For each sequence of words a sequence of lines is produced. The asterisk is used to abstract from the concrete implementation. Like with streams. Whether the list of words gets implemented as an array or an IEnumerable is not important during design. It´s an implementation detail. Does any processing step require further refinement? I don´t think so. They all look pretty “atomic” to me. And if not… I can always backtrack and refine a process step using functional design later once I´ve gained more insight into a sub-problem. Implementation The implementation is straightforward as you can imagine. The processing steps can all be translated into functions. Each can be tested easily and separately. Each has a focused responsibility. And the process flow becomes just a sequence of function calls: Easy to understand. It clearly states how word wrapping works - on a high level of abstraction. And it´s easy to evolve as you´ll see. Flow Design - Increment 2 So far only texts consisting of “average words” are wrapped correctly. Words not fitting in a line will result in lines too long. Wrapping long words is a feature of the requested functionality. Whether it´s there or not makes a difference to the user. To quickly get feedback I decided to first implement a solution without this feature. But now it´s time to add it to deliver the full scope. Fortunately Flow Design automatically leads to code following the Open Closed Principle (OCP). It´s easy to extend it - instead of changing well tested code. How´s that possible? Flow Design allows for extension of functionality by inserting functional units into the flow. That way existing functional units need not be changed. The data flow arrow between functional units is a natural extension point. No need to resort to the Strategy Pattern. No need to think ahead where extions might need to be made in the future. I just “phase in” the remaining processing step: Since neither Extract words nor Reformat know of their environment neither needs to be touched due to the “detour”. The new processing step accepts the output of the existing upstream step and produces data compatible with the existing downstream step. Implementation - Increment 2 A trivial implementation checking the assumption if this works does not do anything to split long words. The input is just passed on: Note how clean WordWrap() stays. The solution is easy to understand. A developer looking at this code sometime in the future, when a new feature needs to be build in, quickly sees how long words are dealt with. Compare this to Robert C. Martin´s solution:[4] How does this solution handle long words? Long words are not even part of the domain language present in the code. At least I need considerable time to understand the approach. Admittedly the Flow Design solution with the full implementation of long word splitting is longer than Robert C. Martin´s. At least it seems. Because his solution does not cover all the “word wrap situations” the Flow Design solution handles. Some lines would need to be added to be on par, I guess. But even then… Is a difference in LOC that important as long as it´s in the same ball park? I value understandability and openness for extension higher than saving on the last line of code. Simplicity is not just less code, it´s also clarity in design. But don´t take my word for it. Try Flow Design on larger problems and compare for yourself. What´s the easier, more straightforward way to clean code? And keep in mind: You ain´t seen all yet ;-) There´s more to Flow Design than described in this chapter. In closing I hope I was able to give you a impression of functional design that makes you hungry for more. To me it´s an inevitable step in software development. Jumping from requirements to code does not scale. And it leads to dirty code all to quickly. Some thought should be invested first. Where there is a clear Entry Point visible, it´s functionality should be designed using data flows. Because with data flows abstraction is possible. For more background on why that´s necessary read my blog article here. For now let me point out to you - if you haven´t already noticed - that Flow Design is a general purpose declarative language. It´s “programming by intention” (Shalloway et al.). Just write down how you think the solution should work on a high level of abstraction. This breaks down a large problem in smaller problems. And by following the PoMO the solutions to those smaller problems are independent of each other. So they are easy to test. Or you could even think about getting them implemented in parallel by different team members. Flow Design not only increases evolvability, but also helps becoming more productive. All team members can participate in functional design. This goes beyon collective code ownership. We´re talking collective design/architecture ownership. Because with Flow Design there is a common visual language to talk about functional design - which is the foundation for all other design activities.   PS: If you like what you read, consider getting my ebook “The Incremental Architekt´s Napkin”. It´s where I compile all the articles in this series for easier reading. I like the strictness of Function Programming - but I also find it quite hard to live by. And it certainly is not what millions of programmers are used to. Also to me it seems, the real world is full of state and side effects. So why give them such a bad image? That´s why functional design takes a more pragmatic approach. State and side effects are ok for processing steps - but be sure to follow the SRP. Don´t put too much of it into a single processing step. ? Image taken from www.physioweb.org ? My code samples are written in C#. C# sports typed function pointers called delegates. Action is such a function pointer type matching functions with signature void someName(T t). Other languages provide similar ways to work with functions as first class citizens - even Java now in version 8. I trust you find a way to map this detail of my translation to your favorite programming language. I know it works for Java, C++, Ruby, JavaScript, Python, Go. And if you´re using a Functional Programming language it´s of course a no brainer. ? Taken from his blog post “The Craftsman 62, The Dark Path”. ?

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• Asp.NET ReportViewer “report execution has expired or cannot be found” error when using session state service or SQL Server session state

  - by dotneteer

  We encountered an error like: ReportServerException: The report execution x5pl2245iwvvq055khsxzlj5 has expired or cannot be found. (rsExecutionNotFound)]    Microsoft.Reporting.WebForms.ServerReportSoapProxy.OnSoapException(SoapException e) +72    Microsoft.Reporting.WebForms.Internal.Soap.ReportingServices2005.Execution.ProxyMethodInvocation.Execute(RSExecutionConnection connection, ProxyMethod`1 initialMethod, ProxyMethod`1 retryMethod) +428    Microsoft.Reporting.WebForms.Internal.Soap.ReportingServices2005.Execution.RSExecutionConnection.GetExecutionInfo() +133    Microsoft.Reporting.WebForms.ServerReport.EnsureExecutionSession() +197    Microsoft.Reporting.WebForms.ServerReport.LoadViewState(Object viewStateObj) +256    Microsoft.Reporting.WebForms.ServerReport..ctor(SerializationInfo info, StreamingContext context) +355 [TargetInvocationException: Exception has been thrown by the target of an invocation.]    System.RuntimeMethodHandle._SerializationInvoke(Object target, SignatureStruct&amp; declaringTypeSig, SerializationInfo info, StreamingContext context) +0    System.Reflection.RuntimeConstructorInfo.SerializationInvoke(Object target, SerializationInfo info, StreamingContext context) +108    System.Runtime.Serialization.ObjectManager.CompleteISerializableObject(Object obj, SerializationInfo info, StreamingContext context) +273    System.Runtime.Serialization.ObjectManager.FixupSpecialObject(ObjectHolder holder) +49    System.Runtime.Serialization.ObjectManager.DoFixups() +223    System.Runtime.Serialization.Formatters.Binary.ObjectReader.Deserialize(HeaderHandler handler, __BinaryParser serParser, Boolean fCheck, Boolean isCrossAppDomain, IMethodCallMessage methodCallMessage) +188    System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Deserialize(Stream serializationStream, HeaderHandler handler, Boolean fCheck, Boolean isCrossAppDomain, IMethodCallMessage methodCallMessage) +203    System.Web.Util.AltSerialization.ReadValueFromStream(BinaryReader reader) +788    System.Web.SessionState.SessionStateItemCollection.ReadValueFromStreamWithAssert() +55    System.Web.SessionState.SessionStateItemCollection.DeserializeItem(String name, Boolean check) +281    System.Web.SessionState.SessionStateItemCollection.DeserializeItem(Int32 index) +110    System.Web.SessionState.SessionStateItemCollection.get_Item(Int32 index) +17    System.Web.SessionState.HttpSessionStateContainer.get_Item(Int32 index) +13    System.Web.Util.AspCompatApplicationStep.OnPageStartSessionObjects() +71    System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2065 This error occurs long after the report viewer page has closed. It occurs to any asp.net page in the application, rendering the entire application unusable until the user gets a new session. The cause of the problem is that the ReportViewer uses session state. When a page retrieves session from any out-of-state session, the session variable of type Microsoft.Reporting.WebForms.ReportHierarchy is deserialized from the session storage. The deserialization could cause the object to connect to the report server when the report is no longer available. The solution is simple but not pretty. We need to clean up the session variable when the report viewer page is closed. One way is to add some Javascript to the page to handle the window.onunload event. In the event handler, call a web service to clean up the session variable. The name of the session variable appears to be randomly generated. So we need to loop through the session variable to find a variable of the type Microsoft.Reporting.WebForms.ReportHierarchy. Microsoft has implemented pinging between the report viewer and the report server to keep the report alive on the server when the report viewer is up; I hope they will go one step further to take care of this problem.

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