return path - Page 408 - Developer IT

Useful Extension Method for ICloneable

- by DesigningCode

In the past, I’ve had to put a type specific clone in each cloneable class, but with extension methods you can write a generic T specific clone class Program { static void Main(string[] args) { var b = new Blah() {X = 1, Y = 2}; var bb = b.Clone(); Console.WriteLine(string.Format("{0} {1}", bb.X, bb.Y)); } } public class Blah : ICloneable { public int X; public int Y; object ICloneable.Clone() { return MemberwiseClone(); } } public static class CloneExtension { public static T Clone<T>(this T o) where T : ICloneable { return (T)o.Clone(); } }

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Using SPServices & jQuery to Find My Stuff from Multi-Select Person/Group Field

- by Mark Rackley

Okay… quick blog post for all you SPServices fans out there. I needed to quickly write a script that would return all the tasks currently assigned to me. I also wanted it to return any task that was assigned to a group I belong to. This can actually be done with a CAML query, so no big deal, right? The rub is that the “assigned to” field is a multi-select person or group field. As far as I know (and I actually know so little) you cannot just write a CAML query to return this information. If you can, please leave a comment below and disregard the rest of this blog post… So… what’s a hacker to do? As always, I break things down to their most simple components (I really love the KISS principle and would get it tattooed on my back if people wouldn’t think it meant “Knights In Satan’s Service”. You really gotta be an old far to get that reference). Here’s what we’re going to do: Get currently logged in user’s name as it is stored in a person field Find all the SharePoint groups the current user belongs to Retrieve a set of assigned tasks from the task list and then find those that are assigned to current user or group current user belongs to Nothing too hairy… So let’s get started Some Caveats before I continue There are some obvious performance implications with this solution as I make a total of four SPServices calls and there’s a lot of looping going on. Also, the CAML query in this blog has NOT been optimized. If you move forward with this code, tweak it so that it returns a further subset of data or you will see horrible performance if you have a few hundred entries in your task list. Add a date range to the CAML or something. Find some way to limit the results as much as possible. Lastly, if you DO have a better solution, I would like you to share. Iron sharpens iron and all… Alright, let’s really get started. Get currently logged in user’s name as it is stored in a person field First thing we need to do is understand how a person group looks when you look at the XML returned from a SharePoint Web Service call. It turns out it’s stored like any other multi select item in SharePoint which is <id>;#<value> and when you assign a person to that field the <value> equals the person’s name “Mark Rackley” in my case. This is for Windows Authentication, I would expect this to be different in FBA, but I’m not using FBA. If you want to know what it looks like with FBA you can use the code in this blog and strategically place an alert to see the value. Anyway… I need to find the name of the user who is currently logged in as it is stored in the person field. This turns out to be one SPServices call: var userName = $().SPServices.SPGetCurrentUser({ fieldName: "Title", debug: false }); As you can see, the “Title” field has the information we need. I suspect (although again, I haven’t tried) that the Title field also contains the user’s name as we need it if I was using FBA. Okay… last thing we need to do is store our users name in an array for processing later: myGroups = new Array(); myGroups.push(userName); Find all the SharePoint groups the current user belongs to Now for the groups. How are groups returned in that XML stream? Same as the person <ID>;#<Group Name>, and if it’s a mutli select it’s all returned in one big long string “<ID>;#<Group Name>;#<ID>;#<Group Name>;#<ID>;#<Group Name>;#<ID>;#<Group Name>;#<ID>;#<Group Name>”. So, how do we find all the groups the current user belongs to? This is also a simple SPServices call. Using the “GetGroupCollectionFromUser” operation we can find all the groups a user belongs to. So, let’s execute this method and store all our groups. $().SPServices({ operation: "GetGroupCollectionFromUser", userLoginName: $().SPServices.SPGetCurrentUser(), async: false, completefunc: function(xData, Status) { $(xData.responseXML).find("[nodeName=Group]").each(function() { myGroups.push($(this).attr("Name")); }); } }); So, all we did in the above code was execute the “GetGroupCollectionFromUser” operation and look for the each “Group” node (row) and store the name for each group in our array that we put the user’s name in previously (myGroups). Now we have an array that contains the current user’s name as it will appear in the person field XML and all the groups the current user belongs to. The Rest Now comes the easy part for all of you familiar with SPServices. We are going to retrieve our tasks from the Task list using “GetListItems” and look at each entry to see if it belongs to this person. If it does belong to this person we are going to store it for later processing. That code looks something like this: // get list of assigned tasks that aren't closed... *modify the CAML to perform better!* $().SPServices({ operation: "GetListItems", async: false, listName: "Tasks", CAMLViewFields: "<ViewFields>" + "<FieldRef Name='AssignedTo' />" + "<FieldRef Name='Title' />" + "<FieldRef Name='StartDate' />" + "<FieldRef Name='EndDate' />" + "<FieldRef Name='Status' />" + "</ViewFields>", CAMLQuery: "<Query><Where><And><IsNotNull><FieldRef Name='AssignedTo'/></IsNotNull><Neq><FieldRef Name='Status'/><Value Type='Text'>Completed</Value></Neq></And></Where></Query>", completefunc: function (xData, Status) { var aDataSet = new Array(); //loop through each returned Task $(xData.responseXML).find("[nodeName=z:row]").each(function() { //store the multi-select string of who task is assigned to var assignedToString = $(this).attr("ows_AssignedTo"); found = false; //loop through the persons name and all the groups they belong to for(var i=0; i<myGroups.length; i++) { //if the person's name or group exists in the assigned To string //then the task is assigned to them if (assignedToString.indexOf(myGroups[i]) >= 0){ found = true; break; } } //if the Task belongs to this person then store or display it //(I'm storing it in an array) if (found){ var thisName = $(this).attr("ows_Title"); var thisStartDate = $(this).attr("ows_StartDate"); var thisEndDate = $(this).attr("ows_EndDate"); var thisStatus = $(this).attr("ows_Status"); var aDataRow=new Array( thisName, thisStartDate, thisEndDate, thisStatus); aDataSet.push(aDataRow); } }); SomeFunctionToDisplayData(aDataSet); } }); Some notes on why I did certain things and additional caveats. You will notice in my code that I’m doing an AssignedToString.indexOf(GroupName) to see if the task belongs to the person. This could possibly return bad results if you have SharePoint Group names that are named in such a way that the “IndexOf” returns a false positive. For example if you have a Group called “My Users” and a group called “My Users – SuperUsers” then if a user belonged to “My Users” it would return a false positive on executing “My Users – SuperUsers”.IndexOf(“My Users”). Make sense? Just be aware of this when naming groups, we don’t have this problem. This is where also some fine-tuning can probably be done by those smarter than me. This is a pretty inefficient method to determine if a task belongs to a user, I mean what if a user belongs to 20 groups? That’s a LOT of looping. See all the opportunities I give you guys to do something fun?? Also, why am I storing my values in an array instead of just writing them out to a Div? Well.. I want to pass my data to a jQuery library to format it all nice and pretty and an Array is a great way to do that. When all is said and done and we put all the code together it looks like: $(document).ready(function() { var userName = $().SPServices.SPGetCurrentUser({ fieldName: "Title", debug: false }); myGroups = new Array(); myGroups.push(userName ); $().SPServices({ operation: "GetGroupCollectionFromUser", userLoginName: $().SPServices.SPGetCurrentUser(), async: false, completefunc: function(xData, Status) { $(xData.responseXML).find("[nodeName=Group]").each(function() { myGroups.push($(this).attr("Name")); }); // get list of assigned tasks that aren't closed... *modify this CAML to perform better!* $().SPServices({ operation: "GetListItems", async: false, listName: "Tasks", CAMLViewFields: "<ViewFields>" + "<FieldRef Name='AssignedTo' />" + "<FieldRef Name='Title' />" + "<FieldRef Name='StartDate' />" + "<FieldRef Name='EndDate' />" + "<FieldRef Name='Status' />" + "</ViewFields>", CAMLQuery: "<Query><Where><And><IsNotNull><FieldRef Name='AssignedTo'/></IsNotNull><Neq><FieldRef Name='Status'/><Value Type='Text'>Completed</Value></Neq></And></Where></Query>", completefunc: function (xData, Status) { var aDataSet = new Array(); //loop through each returned Task $(xData.responseXML).find("[nodeName=z:row]").each(function() { //store the multi-select string of who task is assigned to var assignedToString = $(this).attr("ows_AssignedTo"); found = false; //loop through the persons name and all the groups they belong to for(var i=0; i<myGroups.length; i++) { //if the person's name or group exists in the assigned To string //then the task is assigned to them if (assignedToString.indexOf(myGroups[i]) >= 0){ found = true; break; } } //if the Task belongs to this person then store or display it //(I'm storing it in an array) if (found){ var thisName = $(this).attr("ows_Title"); var thisStartDate = $(this).attr("ows_StartDate"); var thisEndDate = $(this).attr("ows_EndDate"); var thisStatus = $(this).attr("ows_Status"); var aDataRow=new Array( thisName, thisStartDate, thisEndDate, thisStatus); aDataSet.push(aDataRow); } }); SomeFunctionToDisplayData(aDataSet); } }); } }); }); Final Thoughts So, there you have it. Take it and run with it. Make it something cool (and tell me how you did it). Another possible way to improve performance in this scenario is to use a DVWP to display the tasks and use jQuery and the “myGroups” array from this blog post to hide all those rows that don’t belong to the current user. I haven’t tried it, but it does move some of the processing off to the server (generating the view) so it may perform better. As always, thanks for stopping by… hope you have a Merry Christmas…

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Visual Tree Enumeration

- by codingbloke

I feel compelled to post this blog because I find I’m repeatedly posting this same code in silverlight and windows-phone-7 answers in Stackoverflow. One common task that we feel we need to do is burrow into the visual tree in a Silverlight or Windows Phone 7 application (actually more recently I found myself doing this in WPF as well). This allows access to details that aren’t exposed directly by some controls. A good example of this sort of requirement is found in the “Restoring exact scroll position of a listbox in Windows Phone 7” question on stackoverflow. This required that the scroll position of the scroll viewer internal to a listbox be accessed. A caveat One caveat here is that we should seriously challenge the need for this burrowing since it may indicate that there is a design problem. Burrowing into the visual tree or indeed burrowing out to containing ancestors could represent significant coupling between module boundaries and that generally isn’t a good idea. Why isn’t this idea just not cast aside as a no-no? Well the whole concept of a “Templated Control”, which are in extensive use in these applications, opens the coupling between the content of the visual tree and the internal code of a control. For example, I can completely change the appearance and positioning of elements that make up a ComboBox. The ComboBox control relies on specific template parts having set names of a specified type being present in my template. Rightly or wrongly this does kind of give license to writing code that has similar coupling. Hasn’t this been done already? Yes it has. There are number of blogs already out there with similar solutions. In fact if you are using Silverlight toolkit the VisualTreeExtensions class already provides this feature. However I prefer my specific code because of the simplicity principle I hold to. Only write the minimum code necessary to give all the features needed. In this case I add just two extension methods Ancestors and Descendents, note I don’t bother with “Get” or “Visual” prefixes. Also I haven’t added Parent or Children methods nor additional “AndSelf” methods because all but Children is achievable with the addition of some other Linq methods. I decided to give Descendents an additional overload for depth hence a depth of 1 is equivalent to Children but this overload is a little more flexible than simply Children. So here is the code:- VisualTreeEnumeration public static class VisualTreeEnumeration { public static IEnumerable<DependencyObject> Descendents(this DependencyObject root, int depth) { int count = VisualTreeHelper.GetChildrenCount(root); for (int i = 0; i < count; i++) { var child = VisualTreeHelper.GetChild(root, i); yield return child; if (depth > 0) { foreach (var descendent in Descendents(child, --depth)) yield return descendent; } } } public static IEnumerable<DependencyObject> Descendents(this DependencyObject root) { return Descendents(root, Int32.MaxValue); } public static IEnumerable<DependencyObject> Ancestors(this DependencyObject root) { DependencyObject current = VisualTreeHelper.GetParent(root); while (current != null) { yield return current; current = VisualTreeHelper.GetParent(current); } } } Usage examples The following are some examples of how to combine the above extension methods with Linq to generate the other axis scenarios that tree traversal code might require. Missing Axis Scenarios var parent = control.Ancestors().Take(1).FirstOrDefault(); var children = control.Descendents(1); var previousSiblings = control.Ancestors().Take(1) .SelectMany(p => p.Descendents(1).TakeWhile(c => c != control)); var followingSiblings = control.Ancestors().Take(1) .SelectMany(p => p.Descendents(1).SkipWhile(c => c != control).Skip(1)); var ancestorsAndSelf = Enumerable.Repeat((DependencyObject)control, 1) .Concat(control.Ancestors()); var descendentsAndSelf = Enumerable.Repeat((DependencyObject)control, 1) .Concat(control.Descendents()); You might ask why I don’t just include these in the VisualTreeEnumerator. I don’t on the principle of only including code that is actually needed. If you find that one or more of the above is needed in your code then go ahead and create additional methods. One of the downsides to Extension methods is that they can make finding the method you actually want in intellisense harder. Here are some real world usage scenarios for these methods:- Real World Scenarios //Gets the internal scrollviewer of a ListBox ScrollViewer sv = someListBox.Descendents().OfType<ScrollViewer>().FirstOrDefault(); // Get all text boxes in current UserControl:- var textBoxes = this.Descendents().OfType<TextBox>(); // All UIElement direct children of the layout root grid:- var topLevelElements = LayoutRoot.Descendents(0).OfType<UIElement>(); // Find the containing `ListBoxItem` for a UIElement:- var container = elem.Ancestors().OfType<ListBoxItem>().FirstOrDefault(); // Seek a button with the name "PinkElephants" even if outside of the current Namescope:- var pinkElephantsButton = this.Descendents() .OfType<Button>() .FirstOrDefault(b => b.Name == "PinkElephants"); //Clear all checkboxes with the name "Selector" in a Treeview foreach (CheckBox checkBox in elem.Descendents() .OfType<CheckBox>().Where(c => c.Name == "Selector")) { checkBox.IsChecked = false; } The last couple of examples above demonstrate a common requirement of finding controls that have a specific name. FindName will often not find these controls because they exist in a different namescope. Hope you find this useful, if not I’m just glad to be able to link to this blog in future stackoverflow answers.

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How to handle Real Time Data from a database perspective?

- by balexandre

I have an idea in mind, but it still confuses me the database area. Imagine that I want to show real time data, and using one of the latest browser technologies (web sockets - even using older browsers) it is very easy to show to all observables (user browser) what everyone is doing. Remy Sharp has an example about the simplicity about this. But I still don't get the database part, how would I feed, let's imagine (using Remy game Tron) that I want to save the path for each connected user in a database and if a client wants to see what is going on with a 5 sec delay, he will see that, not only the 5 sec until that moment but the continuation in time ... how can I query a DB like that? SELECT x, y FROM run WHERE time >= DATEADD(second, -5, rundate); is not the recommended path right? and pulling this x in x time ... this is not real data feed correct? If can someone help me understand the Database point of view, I would greatly appreciate.

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Drawing a texture at the end of a trace (crosshair?) UDK

- by Dave Voyles

I'm trying to draw a crosshair at the end of my trace. If my crosshair does not hit a pawn or static mesh (ex, just a skybox) then the crosshair stays locked on a certain point at that actor - I want to say its origin. Ex: Run across a pawn, then it turns yellow and stays on that pawn. If it runs across the skybox, then it stays at one point on the box. Weird? How can I get my crosshair to stay consistent? I've included two images for reference, to help illustrate. Note: The wrench is actually my crosshair. The "X" is just a debug crosshair. Ignore that. /// Image 1 /// /// Image 2 /// /*************************************************************************** * Draws the crosshair ***************************************************************************/ function bool CheckCrosshairOnFriendly() { local float CrosshairSize; local vector HitLocation, HitNormal, StartTrace, EndTrace, ScreenPos; local actor HitActor; local MyWeapon W; local Pawn MyPawnOwner; /** Sets the PawnOwner */ MyPawnOwner = Pawn(PlayerOwner.ViewTarget); /** Sets the Weapon */ W = MyWeapon(MyPawnOwner.Weapon); /** If we don't have an owner, then get out of the function */ if ( MyPawnOwner == None ) { return false; } /** If we have a weapon... */ if ( W != None) { /** Values for the trace */ StartTrace = W.InstantFireStartTrace(); EndTrace = StartTrace + W.MaxRange() * vector(PlayerOwner.Rotation); HitActor = MyPawnOwner.Trace(HitLocation, HitNormal, EndTrace, StartTrace, true, vect(0,0,0),, TRACEFLAG_Bullet); DrawDebugLine(StartTrace, EndTrace, 100,100,100,); /** Projection for the crosshair to convert 3d coords into 2d */ ScreenPos = Canvas.Project(HitLocation); /** If we haven't hit any actors... */ if ( Pawn(HitActor) == None ) { HitActor = (HitActor == None) ? None : Pawn(HitActor.Base); } } /** If our trace hits a pawn... */ if ((Pawn(HitActor) == None)) { /** Draws the crosshair for no one - Grey*/ CrosshairSize = 28 * (Canvas.ClipY / 768) * (Canvas.ClipX /1024); Canvas.SetDrawColor(100,100,128,255); Canvas.SetPos(ScreenPos.X - (CrosshairSize * 0.5f), ScreenPos.Y -(CrosshairSize * 0.5f)); Canvas.DrawTile(class'UTHUD'.default.AltHudTexture, CrosshairSize, CrosshairSize, 600, 262, 28, 27); return false; } /** Draws the crosshair for friendlies - Yellow */ CrosshairSize = 28 * (Canvas.ClipY / 768) * (Canvas.ClipX /1024); Canvas.SetDrawColor(255,255,128,255); Canvas.SetPos(ScreenPos.X - (CrosshairSize * 0.5f), ScreenPos.Y -(CrosshairSize * 0.5f)); Canvas.DrawTile(class'UTHUD'.default.AltHudTexture, CrosshairSize, CrosshairSize, 600, 262, 28, 27); return true; }

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Creating classed in JavaScript

- by Renso

Goal:Creating class instances in JavaScript is not available since you define "classes" in js with object literals. In order to create classical classes like you would in c#, ruby, java, etc, with inheritance and instances.Rather than typical class definitions using object literals, js has a constructor function and the NEW operator that will allow you to new-up a class and optionally provide initial properties to initialize the new object with.The new operator changes the function's context and behavior of the return statement.var Person = function(name) { this.name = name;}; //Init the personvar dude= new Person("renso");//Validate the instanceassert(dude instanceof Person);When a constructor function is called with the new keyword, the context changes from global window to a new and empty context specific to the instance; "this" will refer in this case to the "dude" context.Here is class pattern that you will need to define your own CLASS emulation library:var Class = function() { var _class = function() { this.init.apply(this, arguments); }; _class.prototype.init = function(){}; return _class;}var Person a new Class();Person.prototype.init = function() {};var person = new Person;In order for the class emulator to support adding functions and properties to static classes as well as object instances of People, change the emulator:var Class = function() { var _class = function() { this.init.apply(this, arguments); }; _class.prototype.init = function(){}; _class.fn = _class.prototype; _class.fn.parent = _class; //adding class properties _class.extend = function(obj) { var extended = obj.extended; for(var i in obj) { _class[i] = obj[i]; }; if(extended) extended(_class); }; //adding new instances _class.include = function(obj) { var included = obj.included; for(var i in obj) { _class.fn[i] = obj[i]; }; if(included) included(_class); }; return _class;}Now you can use it to create and extend your own object instances://adding static functions to the class Personvar Person = new Class();Person.extend({ find: function(name) {/*....*/}, delete: function(id) {/*....*/},});//calling static function findvar person = Person.find('renso'); //adding properties and functions to the class' prototype so that they are available on instances of the class Personvar Person = new Class;Person.extend({ save: function(name) {/*....*/}, delete: function(id) {/*....*/}});var dude = new Person;//calling instance functiondude.save('renso');

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Where to install boot loader on a Zenbook Prime?

- by Christians

I cannot figure out where to install the boot loader on my Zenbook UX31A Prime. I have installed Ubuntu many times on normal hard drives, but this is the first SSD and I am struggling. Installed Ubuntu 12.04 64-bit selecting "UEFI: general" boot entry. Installation type: Something Else Created partition /sda5 mount as /, /sda6 mount as /home, /sda7 mount as swap Selected /dev/sda for boot loader installation. Other options are /dev/sda, /dev/sda1/dev/sda3 Windows 7 (loader) ... Grub comes up with 6 entries Ubuntu - this runs great Linux 3.2.0-29-generic recovery mode: mode hangs with "fb: conflicting fb hw usae interdrnfb vs EFI VGA - removing generic adapter" memtest86:erro: unknown command `linux 16' memtest86 serial: unknown command `linux 16' Windows 7 (loader) (on /dev/sda3): invalid EFI file path Windows Recovery Environment (on /dev/sda8): unknown command drivemap, invalid EFI file path. My workaround for booting Windows 7 is hitting ESC during boot, windows boot manager comes up and * for booting into Windows 7 I select "WIndows Boot Manager (PO: SanDisk ....". * for booting into Ubuntu I select ubuntu (P0: SanDisk...) How can I boot into Windows from Grub?

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Why do I get an exception when playing multiple sound instances?

- by Boreal

Right now, I'm adding a rudimentary sound engine to my game. So far, I am able to load in a WAV file and play it once, then free up the memory when I close the game. However, the game crashes with a nice ArgumentOutOfBoundsException when I try to play another sound instance. Specified argument was out of the range of valid values. Parameter name: readLength I'm following this tutorial pretty much exactly, but I still keep getting the aforementioned error. Here's my sound-related code. /// <summary> /// Manages all sound instances. /// </summary> public static class Audio { static XAudio2 device; static MasteringVoice master; static List<SoundInstance> instances; /// <summary> /// The XAudio2 device. /// </summary> internal static XAudio2 Device { get { return device; } } /// <summary> /// Initializes the audio device and master track. /// </summary> internal static void Initialize() { device = new XAudio2(); master = new MasteringVoice(device); instances = new List<SoundInstance>(); } /// <summary> /// Releases all XA2 resources. /// </summary> internal static void Shutdown() { foreach(SoundInstance i in instances) i.Dispose(); master.Dispose(); device.Dispose(); } /// <summary> /// Registers a sound instance with the system. /// </summary> /// <param name="instance">Sound instance</param> internal static void AddInstance(SoundInstance instance) { instances.Add(instance); } /// <summary> /// Disposes any sound instance that has stopped playing. /// </summary> internal static void Update() { List<SoundInstance> temp = new List<SoundInstance>(instances); foreach(SoundInstance i in temp) if(!i.Playing) { i.Dispose(); instances.Remove(i); } } } /// <summary> /// Loads sounds from various files. /// </summary> internal class SoundLoader { /// <summary> /// Loads a .wav sound file. /// </summary> /// <param name="format">The decoded format will be sent here</param> /// <param name="buffer">The data will be sent here</param> /// <param name="soundName">The path to the WAV file</param> internal static void LoadWAV(out WaveFormat format, out AudioBuffer buffer, string soundName) { WaveStream wave = new WaveStream(soundName); format = wave.Format; buffer = new AudioBuffer(); buffer.AudioData = wave; buffer.AudioBytes = (int)wave.Length; buffer.Flags = BufferFlags.EndOfStream; } } /// <summary> /// Manages the data for a single sound. /// </summary> public class Sound : IAsset { WaveFormat format; AudioBuffer buffer; /// <summary> /// Loads a sound from a file. /// </summary> /// <param name="soundName">The path to the sound file</param> /// <returns>Whether the sound loaded successfully</returns> public bool Load(string soundName) { if(soundName.EndsWith(".wav")) SoundLoader.LoadWAV(out format, out buffer, soundName); else return false; return true; } /// <summary> /// Plays the sound. /// </summary> public void Play() { Audio.AddInstance(new SoundInstance(format, buffer)); } /// <summary> /// Unloads the sound from memory. /// </summary> public void Unload() { buffer.Dispose(); } } /// <summary> /// Manages a single sound instance. /// </summary> public class SoundInstance { SourceVoice source; bool playing; /// <summary> /// Whether the sound is currently playing. /// </summary> public bool Playing { get { return playing; } } /// <summary> /// Starts a new instance of a sound. /// </summary> /// <param name="format">Format of the sound</param> /// <param name="buffer">Buffer holding sound data</param> internal SoundInstance(WaveFormat format, AudioBuffer buffer) { source = new SourceVoice(Audio.Device, format); source.BufferEnd += (s, e) => playing = false; source.Start(); source.SubmitSourceBuffer(buffer); // THIS IS WHERE THE EXCEPTION IS THROWN playing = true; } /// <summary> /// Releases memory used by the instance. /// </summary> internal void Dispose() { source.Dispose(); } } The exception occurs on line 156 when I am playing the sound: source.SubmitSourceBuffer(buffer);

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Project Euler 3: (Iron)Python

- by Ben Griswold

In my attempt to learn (Iron)Python out in the open, here’s my solution for Project Euler Problem 3. As always, any feedback is welcome. # Euler 3 # http://projecteuler.net/index.php?section=problems&id=3 # The prime factors of 13195 are 5, 7, 13 and 29. # What is the largest prime factor of the number # 600851475143? import time start = time.time() def largest_prime_factor(n): max = n divisor = 2 while (n >= divisor ** 2): if n % divisor == 0: max, n = n, n / divisor else: divisor += 1 return max print largest_prime_factor(600851475143) print "Elapsed Time:", (time.time() - start) * 1000, "millisecs" a=raw_input('Press return to continue')

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Finding furthermost point in game world

- by user13414

I am attempting to find the furthermost point in my game world given the player's current location and a normalized direction vector in screen space. My current algorithm is: convert player world location to screen space multiply the direction vector by a large number (2000) and add it to the player's screen location to get the distant screen location convert the distant screen location to world space create a line running from the player's world location to the distant world location loop over the bounding "walls" (of which there are always 4) of my game world check whether the wall and the line intersect if so, where they intersect is the furthermost point of my game world in the direction of the vector Here it is, more or less, in code: public Vector2 GetFurthermostWorldPoint(Vector2 directionVector) { var screenLocation = entity.WorldPointToScreen(entity.Location); var distantScreenLocation = screenLocation + (directionVector * 2000); var distantWorldLocation = entity.ScreenPointToWorld(distantScreenLocation); var line = new Line(entity.Center, distantWorldLocation); float intersectionDistance; Vector2 intersectionPoint; foreach (var boundingWall in entity.Level.BoundingWalls) { if (boundingWall.Intersects(line, out intersectionDistance, out intersectionPoint)) { return intersectionPoint; } } Debug.Assert(false, "No intersection found!"); return Vector2.Zero; } Now this works, for some definition of "works". I've found that the further out my distant screen location is, the less chance it has of working. When digging into the reasons why, I noticed that calls to Viewport.Unproject could result in wildly varying return values for points that are "far away". I wrote this stupid little "test" to try and understand what was going on: [Fact] public void wtf() { var screenPositions = new Vector2[] { new Vector2(400, 240), new Vector2(400, -2000), }; var viewport = new Viewport(0, 0, 800, 480); var projectionMatrix = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, viewport.Width / viewport.Height, 1, 200000); var viewMatrix = Matrix.CreateLookAt(new Vector3(400, 630, 600), new Vector3(400, 345, 0), new Vector3(0, 0, 1)); var worldMatrix = Matrix.Identity; foreach (var screenPosition in screenPositions) { var nearPoint = viewport.Unproject(new Vector3(screenPosition, 0), projectionMatrix, viewMatrix, worldMatrix); var farPoint = viewport.Unproject(new Vector3(screenPosition, 1), projectionMatrix, viewMatrix, worldMatrix); Console.WriteLine("For screen position {0}:", screenPosition); Console.WriteLine(" Projected Near Point = {0}", nearPoint.TruncateZ()); Console.WriteLine(" Projected Far Point = {0}", farPoint.TruncateZ()); Console.WriteLine(); } } The output I get on the console is: For screen position {X:400 Y:240}: Projected Near Point = {X:400 Y:629.571 Z:599.0967} Projected Far Point = {X:392.9302 Y:-83074.98 Z:-175627.9} For screen position {X:400 Y:-2000}: Projected Near Point = {X:400 Y:626.079 Z:600.7554} Projected Far Point = {X:390.2068 Y:-767438.6 Z:148564.2} My question is really twofold: what am I doing wrong with the unprojection such that it varies so wildly and, thus, does not allow me to determine the corresponding world point for my distant screen point? is there a better way altogether to determine the furthermost point in world space given a current world space location, and a directional vector in screen space?

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Is it OK to use dynamic typing to reduce the amount of variables in scope?

- by missingno

Often, when I am initializing something I have to use a temporary variable, for example: file_str = "path/to/file" file_file = open(file) or regexp_parts = ['foo', 'bar'] regexp = new RegExp( regexp_parts.join('|') ) However, I like to reduce the scope my variables to the smallest scope possible so there is less places where they can be (mis-)used. For example, I try to use for(var i ...) in C++ so the loop variable is confined to the loop body. In these initialization cases, if I am using a dynamic language, I am then often tempted to reuse the same variable in order to prevent the initial (and now useless) value from being used latter in the function. file = "path/to/file" file = open(file) regexp = ['...', '...'] regexp = new RegExp( regexp.join('|') ) The idea is that by reducing the number of variables in scope I reduce the chances to misuse them. However this sometimes makes the variable names look a little weird, as in the first example, where "file" refers to a "filename". I think perhaps this would be a non issue if I could use non-nested scopes begin scope1 filename = ... begin scope2 file = open(filename) end scope1 //use file here //can't use filename on accident end scope2 but I can't think of any programming language that supports this. What rules of thumb should I use in this situation? When is it best to reuse the variable? When is it best to create an extra variable? What other ways do we solve this scope problem?

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Incorrect results for frustum cull

- by DeadMG

Previously, I had a problem with my frustum culling producing too optimistic results- that is, including many objects that were not in the view volume. Now I have refactored that code and produced a cull that should be accurate to the actual frustum, instead of an axis-aligned box approximation. The problem is that now it never returns anything to be in the view volume. As the mathematical support library I'm using does not provide plane support functions, I had to code much of this functionality myself, and I'm not really the mathematical type, so it's likely that I've made some silly error somewhere. As follows is the relevant code: class Plane { public: Plane() { r0 = Math::Vector(0,0,0); normal = Math::Vector(0,1,0); } Plane(Math::Vector p1, Math::Vector p2, Math::Vector p3) { r0 = p1; normal = Math::Cross((p2 - p1), (p3 - p1)); } Math::Vector r0; Math::Vector normal; }; This class represents one plane as a point and a normal vector. class Frustum { public: Frustum( const std::array<Math::Vector, 8>& points ) { planes[0] = Plane(points[0], points[1], points[2]); planes[1] = Plane(points[4], points[5], points[6]); planes[2] = Plane(points[0], points[1], points[4]); planes[3] = Plane(points[2], points[3], points[6]); planes[4] = Plane(points[0], points[2], points[4]); planes[5] = Plane(points[1], points[3], points[5]); } Plane planes[6]; }; The points are passed in order where (the inverse of) each bit of the index of each point indicates whether it's the left, top, and back of the frustum, respectively. As such, I just picked any three points where they all shared one bit in common to define the planes. My intersection test is as follows (based on this): bool Intersects(Math::AABB lhs, const Frustum& rhs) const { for(int i = 0; i < 6; i++) { Math::Vector pvertex = lhs.TopRightFurthest; Math::Vector nvertex = lhs.BottomLeftClosest; if (rhs.planes[i].normal.x <= -0.0f) { std::swap(pvertex.x, nvertex.x); } if (rhs.planes[i].normal.y <= -0.0f) { std::swap(pvertex.y, nvertex.y); } if (rhs.planes[i].normal.z <= -0.0f) { std::swap(pvertex.z, nvertex.z); } if (Math::Dot(rhs.planes[i].r0, nvertex) < 0.0f) { return false; } } return true; } Also of note is that because I'm using a left-handed co-ordinate system, I wrote my Cross function to return the negative of the formula given on Wikipedia. Any suggestions as to where I've made a mistake?

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SQL Server 2008 R2: StreamInsight - User-defined aggregates

- by Greg Low

I'd briefly played around with user-defined aggregates in StreamInsight with CTP3 but when I started working with the new Count Windows, I found I had to have one working. I learned a few things along the way that I hope will help someone. The first thing you have to do is define a class: public class IntegerAverage : CepAggregate < int , int > { public override int GenerateOutput( IEnumerable < int > eventData) { if (eventData.Count() == 0) { return 0; } else { return eventData.Sum()...(read more)

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SSH: Port Forwarding, Firewalls, & Plesk

- by Kian Mayne

I edited my SSH configuration to accept connections on Port 213, as it was one of the few ports that my work firewall allows through. I then restarted sshd and everything was going well. I tested the ssh server locally, and checked the sshd service was listening on port 213; however, I still cannot get it to work outside of localhost. PuTTY gives a connection refused message, and some of the sites that allow check of ports I tried said the port was closed. To me, this is either firewall or port forwarding. But I've already added inbound and outbound exceptions for it. Is this a problem with my server host, or is there something I've missed? My full SSH config file, as requested: # $OpenBSD: sshd_config,v 1.73 2005/12/06 22:38:28 reyk Exp $ # This is the sshd server system-wide configuration file. See # sshd_config(5) for more information. # This sshd was compiled with PATH=/usr/local/bin:/bin:/usr/bin # The strategy used for options in the default sshd_config shipped with # OpenSSH is to specify options with their default value where # possible, but leave them commented. Uncommented options change a # default value. Port 22 Port 213 #Protocol 2,1 Protocol 2 #AddressFamily any #ListenAddress 0.0.0.0 #ListenAddress :: # HostKey for protocol version 1 #HostKey /etc/ssh/ssh_host_key # HostKeys for protocol version 2 #HostKey /etc/ssh/ssh_host_rsa_key #HostKey /etc/ssh/ssh_host_dsa_key # Lifetime and size of ephemeral version 1 server key #KeyRegenerationInterval 1h #ServerKeyBits 768 # Logging # obsoletes QuietMode and FascistLogging #SyslogFacility AUTH SyslogFacility AUTHPRIV #LogLevel INFO # Authentication: #LoginGraceTime 2m #PermitRootLogin yes #StrictModes yes #MaxAuthTries 6 #RSAAuthentication yes #PubkeyAuthentication yes #AuthorizedKeysFile .ssh/authorized_keys # For this to work you will also need host keys in /etc/ssh/ssh_known_hosts #RhostsRSAAuthentication no # similar for protocol version 2 #HostbasedAuthentication no # Change to yes if you don't trust ~/.ssh/known_hosts for # RhostsRSAAuthentication and HostbasedAuthentication #IgnoreUserKnownHosts no # Don't read the user's ~/.rhosts and ~/.shosts files #IgnoreRhosts yes # To disable tunneled clear text passwords, change to no here! #PasswordAuthentication yes #PermitEmptyPasswords no PasswordAuthentication yes # Change to no to disable s/key passwords #ChallengeResponseAuthentication yes ChallengeResponseAuthentication no # Kerberos options #KerberosAuthentication no #KerberosOrLocalPasswd yes #KerberosTicketCleanup yes #KerberosGetAFSToken no # GSSAPI options #GSSAPIAuthentication no GSSAPIAuthentication yes #GSSAPICleanupCredentials yes GSSAPICleanupCredentials yes # Set this to 'yes' to enable PAM authentication, account processing, # and session processing. If this is enabled, PAM authentication will # be allowed through the ChallengeResponseAuthentication mechanism. # Depending on your PAM configuration, this may bypass the setting of # PasswordAuthentication, PermitEmptyPasswords, and # "PermitRootLogin without-password". If you just want the PAM account and # session checks to run without PAM authentication, then enable this but set # ChallengeResponseAuthentication=no #UsePAM no UsePAM yes # Accept locale-related environment variables AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT AcceptEnv LC_IDENTIFICATION LC_ALL #AllowTcpForwarding yes #GatewayPorts no #X11Forwarding no X11Forwarding yes #X11DisplayOffset 10 #X11UseLocalhost yes #PrintMotd yes #PrintLastLog yes #TCPKeepAlive yes #UseLogin no #UsePrivilegeSeparation yes #PermitUserEnvironment no #Compression delayed #ClientAliveInterval 0 #ClientAliveCountMax 3 #ShowPatchLevel no #UseDNS yes #PidFile /var/run/sshd.pid #MaxStartups 10 #PermitTunnel no #ChrootDirectory none # no default banner path #Banner /some/path # override default of no subsystems Subsystem sftp /usr/libexec/openssh/sftp-server

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Have you used the ExecutionValue and ExecValueVariable properties?

The ExecutionValue execution value property and it’s friend ExecValueVariable are a much undervalued feature of SSIS, and many people I talk to are not even aware of their existence, so I thought I’d try and raise their profile a bit. The ExecutionValue property is defined on the base object Task, so all tasks have it available, but it is up to the task developer to do something useful with it. The basic idea behind it is that it allows the task to return something useful and interesting about what it has performed, in addition to the standard success or failure result. The best example perhaps is the Execute SQL Task which uses the ExecutionValue property to return the number of rows affected by the SQL statement(s). This is a very useful feature, something people often want to capture into a variable, and start using the result set options to do. Unfortunately we cannot read the value of a task property at runtime from within a SSIS package, so the ExecutionValue property on its own is a bit of a let down, but enter the ExecValueVariable and we have the perfect marriage. The ExecValueVariable is another property exposed through the task (TaskHost), which lets us select a SSIS package variable. What happens now is that when the task sets the ExecutionValue, the interesting value is copied into the variable we set on the ExecValueVariable property, and a variable is something we can access and do something with. So put simply if the ExecutionValue property value is of interest, make sure you create yourself a package variable and set the name as the ExecValueVariable. Have look at the 3 step guide below: 1 Configure your task as normal, for example the Execute SQL Task, which here calls a stored procedure to do some updates. 2 Create variable of a suitable type to match the ExecutionValue, an integer is used to match the result we want to capture, the number of rows. 3 Set the ExecValueVariable for the task, just select the variable we created in step 2. You need to do this in Properties grid for the task (Short-cut key, select the task and press F4) Now when we execute the sample task above, our variable UpdateQueueRowCount will get the number of rows we updated in our Execute SQL Task. I’ve tried to collate a list of tasks that return something useful via the ExecutionValue and ExecValueVariable mechanism, but the documentation isn’t always great. Task ExecutionValue Description Execute SQL Task Returns the number of rows affected by the SQL statement or statements. File System Task Returns the number of successful operations performed by the task. File Watcher Task Returns the full path of the file found Transfer Error Messages Task Returns the number of error messages that have been transferred Transfer Jobs Task Returns the number of jobs that are transferred Transfer Logins Task Returns the number of logins transferred Transfer Master Stored Procedures Task Returns the number of stored procedures transferred Transfer SQL Server Objects Task Returns the number of objects transferred WMI Data Reader Task Returns an object that contains the results of the task. Not exactly clear, but I assume it depends on the WMI query used.

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How to combine wildcards and spaces (quotes) in an Windows command?

- by Jan Fabry

I want to remove directories of the following format: C:\Program Files\FogBugz\Plugins\cache\[email protected]_NN NN is a number, so I want to use a wildcard (this is part of a post-build step in Visual Studio). The problem is that I need to combine quotes around the path name (for the space in Program Files) with a wildcard to match the end of the path. I already found out that rd is the remove command that accepts wildcards, but where do I put the quotes? I have tried no ending quote (works for dir), ...example.com*", ...example.com"*, ...example.com_??", ...cache\"[email protected]*, ...cache"\[email protected]*, but none of them work. (How many commands to remove a file/directory are there in Windows anyway? And why do they all differ in capabilities?)

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Unable to load memcache.so extension ??

- by billyduc

I built php from source with configure command : './configure' '--prefix=/usr/local/php-5.2.8' '--with-config-file-path=/etc --with-config-file-scan-dir=/etc/php.d' '--with-apxs2=/usr/local/httpd/bin/apxs' '--with-mysql=/usr/local/mysql/' '--with-zlib' I installed php memcache extension : wget http://pecl.php.net/get/memcache tar -zxvf memcache-2.2.5.tgz cd memcache-2.2.5 phpize ./configure --enable-memcache make make install I add to my /usr/local/lib/php.in extension=memcache.so Rebooted my apache and run php-m but php seem doesn't load memcache extension I followed this solution from this site http://www.howtoforge.com/forums/showthread.php?t=26554 I added full path extension=/usr/local/lib/php/extensions/no-debug-non-zts-20060613/memcache.so rebooted apache But it didn't load memcache extension ! I google around but the same issue ! How can I load this extension _ _"

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Azure – Part 5 – Repository Pattern for Table Service

- by Shaun

In my last post I created a very simple WCF service with the user registration functionality. I created an entity for the user data and a DataContext class which provides some methods for operating the entities such as add, delete, etc. And in the service method I utilized it to add a new entity into the table service. But I didn’t have any validation before registering which is not acceptable in a real project. So in this post I would firstly add some validation before perform the data creation code and show how to use the LINQ for the table service. LINQ to Table Service Since the table service utilizes ADO.NET Data Service to expose the data and the managed library of ADO.NET Data Service supports LINQ we can use it to deal with the data of the table service. Let me explain with my current example: I would like to ensure that when register a new user the email address should be unique. So I need to check the account entities in the table service before add. If you remembered, in my last post I mentioned that there’s a method in the TableServiceContext class – CreateQuery, which will create a IQueryable instance from a given type of entity. So here I would create a method under my AccountDataContext class to return the IQueryable<Account> which named Load. 1: public class AccountDataContext : TableServiceContext 2: { 3: private CloudStorageAccount _storageAccount; 4: 5: public AccountDataContext(CloudStorageAccount storageAccount) 6: : base(storageAccount.TableEndpoint.AbsoluteUri, storageAccount.Credentials) 7: { 8: _storageAccount = storageAccount; 9: 10: var tableStorage = new CloudTableClient(_storageAccount.TableEndpoint.AbsoluteUri, 11: _storageAccount.Credentials); 12: tableStorage.CreateTableIfNotExist("Account"); 13: } 14: 15: public void Add(Account accountToAdd) 16: { 17: AddObject("Account", accountToAdd); 18: SaveChanges(); 19: } 20: 21: public IQueryable<Account> Load() 22: { 23: return CreateQuery<Account>("Account"); 24: } 25: } The method returns the IQueryable<Account> so that I can perform the LINQ operation on it. And back to my service class, I will use it to implement my validation. 1: public bool Register(string email, string password) 2: { 3: var storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString"); 4: var accountToAdd = new Account(email, password) { DateCreated = DateTime.Now }; 5: var accountContext = new AccountDataContext(storageAccount); 6: 7: // validation 8: var accountNumber = accountContext.Load() 9: .Where(a => a.Email == accountToAdd.Email) 10: .Count(); 11: if (accountNumber > 0) 12: { 13: throw new ApplicationException(string.Format("Your account {0} had been used.", accountToAdd.Email)); 14: } 15: 16: // create entity 17: try 18: { 19: accountContext.Add(accountToAdd); 20: return true; 21: } 22: catch (Exception ex) 23: { 24: Trace.TraceInformation(ex.ToString()); 25: } 26: return false; 27: } I used the Load method to retrieve the IQueryable<Account> and use Where method to find the accounts those email address are the same as the one is being registered. If it has I through an exception back to the client side. Let’s run it and test from my simple client application. Oops! Looks like we encountered an unexpected exception. It said the “Count” is not support by the ADO.NET Data Service LINQ managed library. That is because the table storage managed library (aka. TableServiceContext) is based on the ADO.NET Data Service and it supports very limit LINQ operation. Although I didn’t find a full list or documentation about which LINQ methods it supports I could even refer a page on msdn here. It gives us a roughly summary of which query operation the ADO.NET Data Service managed library supports and which doesn't. As you see the Count method is not in the supported list. Not only the query operation, there inner lambda expression in the Where method are limited when using the ADO.NET Data Service managed library as well. For example if you added (a => !a.DateDeleted.HasValue) in the Where method to exclude those deleted account it will raised an exception said "Invalid Input". Based on my experience you should always use the simple comparison (such as ==, >, <=, etc.) on the simple members (such as string, integer, etc.) and do not use any shortcut methods (such as string.Compare, string.IsNullOrEmpty etc.). 1: // validation 2: var accountNumber = accountContext.Load() 3: .Where(a => a.Email == accountToAdd.Email) 4: .ToList() 5: .Count; 6: if (accountNumber > 0) 7: { 8: throw new ApplicationException(string.Format("Your account {0} had been used.", accountToAdd.Email)); 9: } We changed the a bit and try again. Since I had created an account with my mail address so this time it gave me an exception said that the email had been used, which is correct. Repository Pattern for Table Service The AccountDataContext takes the responsibility to save and load the account entity but only for that specific entity. Is that possible to have a dynamic or generic DataContext class which can operate any kinds of entity in my system? Of course yes. Although there's no typical database in table service we can threat the entities as the records, similar with the data entities if we used OR Mapping. As we can use some patterns for ORM architecture here we should be able to adopt the one of them - Repository Pattern in this example. We know that the base class - TableServiceContext provide 4 methods for operating the table entities which are CreateQuery, AddObject, UpdateObject and DeleteObject. And we can create a relationship between the enmity class, the table container name and entity set name. So it's really simple to have a generic base class for any kinds of entities. Let's rename the AccountDataContext to DynamicDataContext and make the type of Account as a type parameter if it. 1: public class DynamicDataContext<T> : TableServiceContext where T : TableServiceEntity 2: { 3: private CloudStorageAccount _storageAccount; 4: private string _entitySetName; 5: 6: public DynamicDataContext(CloudStorageAccount storageAccount) 7: : base(storageAccount.TableEndpoint.AbsoluteUri, storageAccount.Credentials) 8: { 9: _storageAccount = storageAccount; 10: _entitySetName = typeof(T).Name; 11: 12: var tableStorage = new CloudTableClient(_storageAccount.TableEndpoint.AbsoluteUri, 13: _storageAccount.Credentials); 14: tableStorage.CreateTableIfNotExist(_entitySetName); 15: } 16: 17: public void Add(T entityToAdd) 18: { 19: AddObject(_entitySetName, entityToAdd); 20: SaveChanges(); 21: } 22: 23: public void Update(T entityToUpdate) 24: { 25: UpdateObject(entityToUpdate); 26: SaveChanges(); 27: } 28: 29: public void Delete(T entityToDelete) 30: { 31: DeleteObject(entityToDelete); 32: SaveChanges(); 33: } 34: 35: public IQueryable<T> Load() 36: { 37: return CreateQuery<T>(_entitySetName); 38: } 39: } I saved the name of the entity type when constructed for performance matter. The table name, entity set name would be the same as the name of the entity class. The Load method returned a generic IQueryable instance which supports the lazy load feature. Then in my service class I changed the AccountDataContext to DynamicDataContext and that's all. 1: var accountContext = new DynamicDataContext<Account>(storageAccount); Run it again and register another account. The DynamicDataContext now can be used for any entities. For example, I would like the account has a list of notes which contains 3 custom properties: Account Email, Title and Content. We create the note entity class. 1: public class Note : TableServiceEntity 2: { 3: public string AccountEmail { get; set; } 4: public string Title { get; set; } 5: public string Content { get; set; } 6: public DateTime DateCreated { get; set; } 7: public DateTime? DateDeleted { get; set; } 8: 9: public Note() 10: : base() 11: { 12: } 13: 14: public Note(string email) 15: : base(email, string.Format("{0}_{1}", email, Guid.NewGuid().ToString())) 16: { 17: AccountEmail = email; 18: } 19: } And no need to tweak the DynamicDataContext we can directly go to the service class to implement the logic. Notice here I utilized two DynamicDataContext instances with the different type parameters: Note and Account. 1: public class NoteService : INoteService 2: { 3: public void Create(string email, string title, string content) 4: { 5: var storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString"); 6: var accountContext = new DynamicDataContext<Account>(storageAccount); 7: var noteContext = new DynamicDataContext<Note>(storageAccount); 8: 9: // validate - email must be existed 10: var accounts = accountContext.Load() 11: .Where(a => a.Email == email) 12: .ToList() 13: .Count; 14: if (accounts <= 0) 15: throw new ApplicationException(string.Format("The account {0} does not exsit in the system please register and try again.", email)); 16: 17: // save the note 18: var noteToAdd = new Note(email) { Title = title, Content = content, DateCreated = DateTime.Now }; 19: noteContext.Add(noteToAdd); 20: } 21: } And updated our client application to test the service. I didn't implement any list service to show all notes but we can have a look on the local SQL database if we ran it at local development fabric. Summary In this post I explained a bit about the limited LINQ support for the table service. And then I demonstrated about how to use the repository pattern in the table service data access layer and make the DataContext dynamically. The DynamicDataContext I created in this post is just a prototype. In fact we should create the relevant interface to make it testable and for better structure we'd better separate the DataContext classes for each individual kind of entity. So it should have IDataContextBase<T>, DataContextBase<T> and for each entity we would have class AccountDataContext<Account> : IDataContextBase<Account>, DataContextBase<Account> { … } class NoteDataContext<Note> : IDataContextBase<Note>, DataContextBase<Note> { … } Besides the structured data saving and loading, another common scenario would be saving and loading some binary data such as images, files. In my next post I will show how to use the Blob Service to store the bindery data - make the account be able to upload their logo in my example. Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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Troubleshooting a crash with Windows 7

- by AngryHacker

I have a folder with several thousand videos (All .MPG extensions). When I open the folder with these videos, it shows up fine, but as I start scrolling down, it crashes the Windows Explorer. In the Event Viewer, I see this: Faulting application name: Explorer.EXE, version: 6.1.7600.16450, time stamp: 0x4aebab8d Faulting module name: ntdll.dll, version: 6.1.7600.16559, time stamp: 0x4ba9b802 Exception code: 0xc0000374 Fault offset: 0x00000000000c6df2 Faulting process id: 0x954 Faulting application start time: 0x01cbb1b71edf3b51 Faulting application path: C:\Windows\Explorer.EXE Faulting module path: C:\Windows\SYSTEM32\ntdll.dll Report Id: ee987372-1dc4-11e0-8e06-406186ea9135 I suspect that one of the videos has bad metadata. I removed the Length column and it was still crashing. I then removed the Date column and the problem disappeared. How do I go about troubleshooting this problem or at least identifying the file that's causing the issue.

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Perl script rendered in browser as code through symlink - fine when accessed directly

- by John Dittmar

I have a Rails 4 app that has some views that post to Perl cgi scripts. The perl scripts are accessed via a symbolic link to a folder called "cgi-bin". When I navigate to a perl script through the symbolic link they are rendered as text instead of executed (ie: localhost:3000/cgi-bin/test.cgi), however when I access them directly they execute without issue (ie. localhost/path/to/cgi-bin/test.cgi). I am using apache2 on os x. In the directory localhost/path/to/ I have an .htaccess file that contains the following: # General Apache options AddHandler fastcgi-script .fcgi AddHandler cgi-script .cgi Options +FollowSymLinks +ExecCGI I have the exact same lines in the .htaccess file that I have in localhost:3000/ I have also uncommented the AllowOverride all in httpd.conf. The are no errors in apache's error log. When I access the direct link to test.cgi a new line is appended to apache's access log, when I access the script through the symbolic link (and it is rendered as text), there is no line appended to the access log. Any idea why this error occurs? This setup worked fine in a previous version of rails of OS X, but recently I upgraded to Mavericks and figured I should update the Rails application to v4.0 as well.

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Let a model instance choose appropriate view class using category. Is it good design?

- by Denis Mikhaylov

Assume I have abstract base model class called MoneySource. And two realizations BankCard and CellularAccount. In MoneysSourceListViewController I want to display a list of them, but with ListItemView different for each MoneySource subclass. What if I define a category on MoneySource @interface MoneySource (ListItemView) - (Class)listItemViewClass; @end And then override it for each concrete sublcass of MoneySource, returning suitable view class. @implementation CellularAccount (ListItemView) - (Class)listItemViewClass { return [BankCardListView class]; } @end @implementation BankCard (ListItemView) - (Class)listItemViewClass { return [CellularAccountListView class]; } @end so I can ask model object about its view, not violating MVC principles, and avoiding class introspection or if constructions. Thank you!

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Automatically mount a remote folder on boot

- by Andrew

I'm trying to mount a Windows folder on my Ubuntu machine on start up. I've tried following this page here, modifying /etc/fstab and appending sshfs#my_user@remote_host:/path/to/directory <local_mount_point> fuse user 0 0 to it, but it fails; on start up, I get an error saying that the mounting failed, and I can press S to skip or M to recover manually. I also tried following this page here, appending /usr/bin/sshfs -o idmap=user my_user@remote_host:/path/to/directory <local_mount_point> to the /etc/rc.local file, but this doesn't help either; Ubuntu just boots up normally without mounting. I have Cygwin installed on my Windows machine, and I can run everything smoothly, such as sshing without passwords, and mounting it manually. I've also tried to run the modified rc.local file $ /etc/rc.local, and it works perfectly, but I just can't seem to get the folder mounted on start up. Can someone help me?

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how to fix fatal error jvmti.h No such file or directory compilation terminated on c code ubuntu? [on hold]

- by Blue Rose

how to fix fatal error jvmti.h No such file or directory compilation terminated c code ubuntu? my c code is: #include "jvmti.h" JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM *jvm, char *options, void *reserved) { /* We return JNI_OK to signify success */ printf("\nBushra Za'areer,\n\n"); return JNI_OK; } JNIEXPORT void JNICALL Agent_OnUnload(JavaVM *vm) { } type this command in terminal: gcc -Wall -W -Werror first_agent.c -o firstagent first_agent.c:1:19: fatal error: jvmti.h: No such file or directory compilation terminated. where java jdk version javac 1.7.0_25 where gcc version gcc version 4.7.3 (Ubuntu/Linaro 4.7.3-2ubuntu4) here should update gcc version to 4.8?

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Launch apps or run commands on Windows via shortcuts

- by Francisc

Is it possible to register shortcuts on Windows 7 so that regardless where you are looking (Desktop, a folder etc) the shortcut gets "heard" and the appropriate action is performed. For example, creating a shortcut in the System32 folder which will work if you use Run with the shortcut's name, will not work if you set a key combination when focus is set on the Desktop for example. Is there a native way of registering top-level shortcuts or even an application for enabling this? Example of things I want keyboard shortcuts for: open a specific folder like %path% create a new .js file in the current folder launch an application eventually with its path set to the current location if the app supports this (e.g. command prompt) Thank you.

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Have apache choose a php version based on the extension in the url, but with a single file on the filesystem

- by Somejan

I want to configure a local apache server to serve php files with different php versions. In my document root I have phpinfo.php, now if I go to http://localhost/phpinfo.php4, I want to see the phpinfo.php file processed with php4, if I go to http://localhost/phpinfo.php5 I want to see the same file processed with php5. Note: both php 4 and 5 are already installed side by side, I have no problem configuring apache to treat files that have a .php4 or .php5 extension on the filesystem with the correct php version. What I want is for apache to do the following: If the url-path ends in .php5, serve the file which has a .php extension on the filesystem using the application/x-httpd-php5 handler. If the url-path ends in .php4, serve the same file with the .php extension on the filesystem using the application/x-httpd-php4 handler.

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