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• C# inherit from a class in a different DLL

  - by Onno

  I need to make an application that needs to be highly modular and that can easily be expanded with new functionality. I've thought up a design where I have a main window and a list of actions that are implemented using a strategy pattern. I'd like to implement the base classes/interfaces in a DLL and have the option of loading actions from DLL's which are loaded dynamically when the application starts. This way the main window can initiate actions without having to recompile or redistribute a new version. I just have to (re)distribute new DLL's which I can update dynamically at runtime. This should enable very easy modular updating from a central online source. The 'action' DLL's all inherit their structure from the code defined in the the DLL which defines the main strategy pattern structure and it's abstract factory. I'd like to know if C# /.Net will allow such a construction. I'd also like to know whether this construction has any major problems in terms of design.

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• CAsyncSocket and ThreadPool problem

  - by zabulus

  I have a server application with such structure: There is one object, call him Server, that in endless cycle listens and accepts connections. I have descendant class from CAsyncSocket, that has overriden event OnReceive, call him ProxySocket. Also I have a thread pool with early created threads. When connection is received by server object he accepts the new connection on the new object ProxySocket. When data arrives to the ProxySocket, he creates a command object and gives it to thread pool. In this command object I giving the socket handle of a ProxySocket. When new object of command is creating - I creating a new Socket in working thread and attach handle to it. My issue is next: When command ends, socket doesn't close, I just detach handle it and set CSocket handle to INVALID_SOCKET value, as planned. But my first ProxySocket object doesn't receives messages of new data receiving after that. How can I solve this?

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• Error while running Scheduled Task from MSBUILD script

  - by SVI

  I am running a MSBUILD script which disables and enabled a scheduled task from command line. I am getting following error. No idea, what 'exited with code 1' means. When I try to copy paste the line in command prompt, it works perfectly. I doesnot run in MSBuild script which is in turn called by CruiseControl.NET SNIPPET FROM MSBUILD file is ERROR is The command "C:\WINDOWS\system32\schtasks.exe /S servername /Change /RU SYSTEM /TN "MyScheduledtask" /DISABLE" exited with code 1.

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• Who should control navigation in an MVVM application?

  - by SonOfPirate

  Example #1: I have a view displayed in my MVVM application (let's use Silverlight for the purposes of the discussion) and I click on a button that should take me to a new page. Example #2: That same view has another button that, when clicked, should open up a details view in a child window (dialog). We know that there will be Command objects exposed by our ViewModel bound to the buttons with methods that respond to the user's click. But, what then? How do we complete the action? Even if we use a so-called NavigationService, what are we telling it? To be more specific, in a traditional View-first model (like URL-based navigation schemes such as on the web or the SL built-in navigation framework) the Command objects would have to know what View to display next. That seems to cross the line when it comes to the separation of concerns promoted by the pattern. On the other hand, if the button wasn't wired to a Command object and behaved like a hyperlink, the navigation rules could be defined in the markup. But do we want the Views to control application flow and isn't navigation just another type of business logic? (I can say yes in some cases and no in others.) To me, the utopian implementation of the MVVM pattern (and I've heard others profess this) would be to have the ViewModel wired in such a way that the application can run headless (i.e. no Views). This provides the most surface area for code-based testing and makes the Views a true skin on the application. And my ViewModel shouldn't care if it displayed in the main window, a floating panel or a child window, should it? According to this apprach, it is up to some other mechanism at runtime to 'bind' what View should be displayed for each ViewModel. But what if we want to share a View with multiple ViewModels or vice versa? So given the need to manage the View-ViewModel relationship so we know what to display when along with the need to navigate between views, including displaying child windows / dialogs, how do we truly accomplish this in the MVVM pattern?

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• Asynchronous update design/interaction patterns

  - by Andy Waite

  These days many apps support asynchronous updates. For example, if you're looking at a list of widgets and you delete one of them then rather than wait for the roundtrip to the server, the app can hide the one you deleted, giving immediate feedback. The actual deletion on the server will happen in the background. This can be seen in web apps, desktop apps, iOS apps, etc. But what about when the background operation fails. How should you feed back to the user? Should you restore the UI to the pre-deletion state? What about when multiple background operations fail together? Does this behaviour/pattern have a name? Perhaps something based on the Command pattern?

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• Is There a Real Advantage to Generic Repository?

  - by Sam

  Was reading through some articles on the advantages of creating Generic Repositories for a new app (example). The idea seems nice because it lets me use the same repository to do several things for several different entity types at once: IRepository repo = new EfRepository(); // Would normally pass through IOC into constructor var c1 = new Country() { Name = "United States", CountryCode = "US" }; var c2 = new Country() { Name = "Canada", CountryCode = "CA" }; var c3 = new Country() { Name = "Mexico", CountryCode = "MX" }; var p1 = new Province() { Country = c1, Name = "Alabama", Abbreviation = "AL" }; var p2 = new Province() { Country = c1, Name = "Alaska", Abbreviation = "AK" }; var p3 = new Province() { Country = c2, Name = "Alberta", Abbreviation = "AB" }; repo.Add<Country>(c1); repo.Add<Country>(c2); repo.Add<Country>(c3); repo.Add<Province>(p1); repo.Add<Province>(p2); repo.Add<Province>(p3); repo.Save(); However, the rest of the implementation of the Repository has a heavy reliance on Linq: IQueryable<T> Query(); IList<T> Find(Expression<Func<T,bool>> predicate); T Get(Expression<Func<T,bool>> predicate); T First(Expression<Func<T,bool>> predicate); //... and so on This repository pattern worked fantastic for Entity Framework, and pretty much offered a 1 to 1 mapping of the methods available on DbContext/DbSet. But given the slow uptake of Linq on other data access technologies outside of Entity Framework, what advantage does this provide over working directly with the DbContext? I attempted to write a PetaPoco version of the Repository, but PetaPoco doesn't support Linq Expressions, which makes creating a generic IRepository interface pretty much useless unless you only use it for the basic GetAll, GetById, Add, Update, Delete, and Save methods and utilize it as a base class. Then you have to create specific repositories with specialized methods to handle all the "where" clauses that I could previously pass in as a predicate. Is the Generic Repository pattern useful for anything outside of Entity Framework? If not, why would someone use it at all instead of working directly with Entity Framework? Edit: Original link doesn't reflect the pattern I was using in my sample code. Here is an (updated link).

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• InvalidOperationException when executing SqlCommand with transaction

  - by Serhat Özgel

  I have this code, running parallel in two separate threads. It works fine for a few times, but at some random point it throws InvalidOperationException: The transaction is either not associated with the current connection or has been completed. At the point of exception, I am looking inside the transaction with visual studio and verify its connection is set normally. Also command.Transaction._internalTransaction. _transactionState is set to Active and IsZombied property is set to false. This is a test application and I am using Thread.Sleep for creating longer transactions and causing overlaps. Why may the exception being thrown and what can I do about it? IDbCommand command = new SqlCommand("Select * From INFO"); IDbConnection connection = new SqlConnection(connectionString); command.Connection = connection; IDbTransaction transaction = null; try { connection.Open(); transaction = connection.BeginTransaction(); command.Transaction = transaction; command.ExecuteNonQuery(); // Sometimes throws exception Thread.Sleep(forawhile); // For overlapping transactions running in parallel transaction.Commit(); } catch (ApplicationException exception) { if (transaction != null) { transaction.Rollback(); } } finally { connection.Close(); }

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• Using Dependency Injection to Work with MessageBoxes in an MVVM Application

  Reviews a simple and testable way to show a MessageBox in any WPF or Silverlight application built with the MVVM design pattern

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• Design patterns for effects between actors and technology

  - by changelog

  I'm working on my first game, and taking the opportunity to brush up my C++ (I want to make as much of it as portable as I can.) Whilst working on the technology tree and how it affects actors (spaceships, planets, crew, buildings, etc) I can't find a pattern that decouples these entities enough to feel like a clean approach. Just as an idea, here's the type of effects these actors can have on one another (and techs too) An engineer inside a spaceship boosts its shield A hero in a spaceship in a fleet increases morale A technology improves spaceships' travel distance A building in a planet improves its production The best I can come up with is the Observer pattern, and basically manage it more or less manually (when a crew member enters a spaceship, fire the event; when a new building is built in a planet, fire the event, etc etc.) but it seems to be too tightly coupled to me. I would love to get some ideas about how to approach this better.

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• How to make xlock use the first key I hit as a part of my password

  - by alesplin

  I just switched from Arch Linux to Ubuntu 10.10. I'm running the Fluxbox window manager, and I use xlockmore to lock my screen with the following key shortcut: 192 :Exec xlock-mode marquee +usefirst -icongeometry 240x240 -message "back in a minute..." The problem I'm having is that xlock is definitely not using my first key as part of my password. Instead, it uses some randomized fade pattern to fade to the password screen. I find this highly annoying, as when I get back to my desk and start entering my password it doesn't register password characters until the fade pattern is complete. I've also tried the following modifications with no difference: 192 :Exec xlock -mode marquee -usefirst -icongeometry 240x240 -message "back in a minute..." 192 :Exec xlock -mode marquee -icongeometry 240x240 -message "back in a minute..." The first example worked flawlessly on Arch. Does Ubuntu have some sort of system default that you can't override on the command-line?

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• Cannot mock class with constructor having array parameter using Rhino Mocks

  - by SharePoint Newbie

  Hi, We cannot mock his class in RhinoMocks. public class Service { public Service(Command[] commands){} } public abstract class Command {} // Code var mock = MockRepository.GenerateMock<Service>(new Command[]{}); // or mock = MockRepository.GenerateMock<Service>(null) Rhino mocks fails complaining that it cannot find a constructor with matching arguments. What am I doing wrong? Thanks,

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• How to automate building and deploying a BPEL application

  - by Juan Manuel Formoso

  I need to automate the building and deployment of (several) BPEL applications to a weblogic server. I now do it using jDeveloper 11g, but I guess there should be some command line tools to do it. (I come from a Microsoft /.NET / Visual Studio background, and I can automate the deployment of my .NET applications using the command line and msbuild) Does anyone know how to do that via the command line?

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• java.util.concurrent.ThreadPoolExecutor strange logic

  - by rodrigoap

  Look ath this method of ThreadPoolExcecutor: public void execute(Runnable command) { ... if (runState == RUNNING && workQueue.offer(command)) { if (runState != RUNNING || poolSize == 0) ensureQueuedTaskHandled(command); } ... } It check that runState is RUNNING and then the oposite. As I'm trying to do some tuning on a SEDA like model I wanted to understand the internals of the thread pool. Do you think this code is correct?

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• What the best way to wire up Entity Framework database context (model) to ViewModel in MVVM WPF?

  - by hal9k2

  As in the question above: What the best way to wire up Entity Framework database model (context) to viewModel in MVVM (WPF)? I am learning MVVM pattern in WPF, alot of examples shows how to implement model to viewModel, but models in that examples are just simple classes, I want to use MVVM together with entity framework model (base first approach). Whats the best way to wire model to viewModel. Thanks for answers. //ctor of ViewModel public ViewModel() { db = new PackageShipmentDBEntities(); // Entity Framework generated class ListaZBazy = new ObservableCollection<Pack>(db.Packs.Where(w => w.IsSent == false)); } This is my usual ctor of ViewModel, think there is a better way, I was reading about repository pattern, not sure if I can adapt this to WPF MVVM

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• Joining different models in Django

  - by Andrew Roberts

  Let's say I have this data model: class Workflow(models.Model): ... class Command(models.Model): workflow = models.ForeignKey(Workflow) ... class Job(models.Model): command = models.ForeignKey(Command) ... Suppose somewhere I want to loop through all the Workflow objects, and for each workflow I want to loop through its Commands, and for each Command I want to loop through each Job. Is there a way to structure this with a single query? That is, I'd like Workflow.objects.all() to join in its dependent models, so I get a collection that has dependent objects already cached, so workflows[0].command_set.get() doesn't produce an additional query. Is this possible?

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• How can I pull an existing heroku app to new location for development?

  - by DJTripleThreat

  Whats the command to do this?

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• Another Custom Property Locator: a Library of Books

  - by Cindy McMullen

  Introduction The previous post gave an introduction to custom property locators and showed how create one using JDeveloper.  This post continues on the custom locator theme, with a slightly more complex locator: a library of books.  It demonstrates using the DAO pattern to delegate data access from the Locator, which is likely how many actual backing stores will integrate with the Locator.  You can imagine, rather than a library of books, the data store might be a user database of sorts.  The same sort of pattern would apply. This post uses the BookLocator example originally shown in the WebCenter documentation, but has: updated the source code to reflect the final Property APIs includes the steps for generating the namespace and property definition files via JDeveloper detailed usage of the PropertyService APIs Getting Started If you're new to JDeveloper, you might want to check out this tutorial.  There is also the "Jump-Start to using Personalization" blog post that you might find useful.  Otherwise, if you're already familiar with both, you can skip those tutorials and jump right in to using JDeveloper. Download the BookLocator.zip file (which has been updated from the original post) and unzip it to a new directory.  Start JDeveloper, navigate to the BookLocator.jws file, and open it.   It should look something like this: The Properties Namespace file contains the property definitions and property set definitions you define.  It is explained more in detail in the Namespace documentation.  Although this example doesn't show it, the property set definitions have the ability to reference multiple locators per property.   This can be done by right-clicking on the 'Locator Info' box.  Configure the contents of the Locator Map  by editing locators and mapping them to available property names in the property set definition. Compiling, deploying, and running your locator The rest of the steps in this tutorial basically follow those in the previous blog on custom locators, and won't be repeated here.   A scenario to invoke your locator is included with the sample app: see BookProperties.scenarios_diagram above.  Summary This post demonstrates a simple library of books accessed by the BookPropertyLocator via the DAO layer.  This is a useful pattern for more realistic property retrievals, such as a backing user store.  It also points out the possibility of retrieving properties from multiple locators, which would be quite handy to retrieve user attributes from multiple sources.

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• How essential is it to make a service layer?

  - by BornToCode

  I started building an app in 3 layers (DAL, BL, UI) [it mainly handles CRM, some sales reports and inventory]. A colleague told me that I must move to service layer pattern, that developers came to service pattern from their experience and it is the better approach to design most applications. He said it would be much easier to maintain the application in the future that way. Personally, I get the feeling that it's just making things more complex and I couldn't see much of a benefit from it that would justify that. This app does have an additional small partial ui that uses some (but only few) of the desktop application functions so I did find myself duplicating some code (but not much). Just because of some code duplication I wouldn't convert it to be service oriented, but he said I should use it anyway because in general it's a very good architecture, why programmers are so in love with services?? I tried to google on it but I'm still confused and can't decide what to do.

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• problem withAsync SqlComman

  - by Alibm

  I have problem with Timeout, when I run a command through app, a timeout exception is thrown, but when I run i directly in sql there is no timeout exception! my SP take about 11 min when I run it directly. for solving this issue, I found below code here, but I doesn't work properly! Immediately after beginExecute, IAsyncResult.iscomplete become true !!!! where is the problem ? IAsyncResult result = command.BeginExecuteNonQuery(); int count = 0; while (!result.IsCompleted) { Console.WriteLine("Waiting ({0})", count++); System.Threading.Thread.Sleep(1000); } Console.WriteLine("Command complete. Affected {0} rows.", command.EndExecuteNonQuery(result)); regards

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• How to remove files and directories quickly

  - by None

  I am using a mac. When I use the "rm" command it can only remove files. The "rmdir" command only removes empty folders. If you have a directory with files and folders with files and folders in them and so on. Is there anyway to delete all the files and folders without all the strenuous command typing? Remember, I am using the mac bash shell from terminal, not Microsoft DOS or linux.

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• Working with complex objects in Prevayler commands

  - by alexantd

  The demos included in the Prevayler distribution show how to pass in a couple strings (or something simple like that) into a command constructor in order to create or update an object. The problem is that I have an object called MyObject that has a lot of fields. If I had to pass all of them into the CreateMyObject command manually, it would be a pain. So an alternative I thought of is to pass my business object itself into the command, but to hang onto a clone of it (keeping in mind that I can't store the BO directly in the command). Of course after executing this command, I would need to make sure to dispose of the original copy that I passed in. public class CreateMyObject implements TransactionWithQuery { private MyObject object; public CreateMyObject(MyObject business_obj) { this.object = (MyObject) business_obj.clone(); } public Object executeAndQuery(...) throws Exception { ... } } The Prevayler wiki says: Transactions can't carry direct object references (pointers) to business objects. This has become known as the baptism problem because it's a common beginner pitfall. Direct object references don't work because once a transaction has been serialized to the journal and then deserialized for execution its object references no longer refer to the intended objects - - any objects they may have referred to at first will have been copied by the serialization process! Therefore, a transaction must carry some kind of string or numeric identifiers for any objects it wants to refer to, and it must look up the objects when it is executed. I think by cloning the passed-in object I will be getting around the "direct object pointer" problem, but I still don't know whether or not this is a good idea...

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• How to make that the LanguageBinder take precedence over the DynamicBinder

  - by rudimenter

  Hi I Have a class which implement IDynamicMetaObjectProvider I implement the BindGetMember Method from DynamicMetaObject. Now when i Generate a dynamic Object and Access a property every call gets implicit passed through the BindGetMember Method. I want that at first the language Binder get his chance before my code comes in. It is somehow doable with "binder.FallbackGetMember" but i am not sure how the expression has to look like. I call here dynamic com=CommandFactory.GetCommand(); com.testprop; //expected: "test"; but "test2" comes back public class Command : System.Dynamic.IDynamicMetaObjectProvider { public string testprop { get { return "test"; } } public object GetValue(string name) { return "test2"; } System.Dynamic.DynamicMetaObject System.Dynamic.IDynamicMetaObjectProvider.GetMetaObject(System.Linq.Expressions.Expression parameter) { return new MetaCommand(parameter, this); } private class MetaCommand : System.Dynamic.DynamicMetaObject { public MetaCommand(Expression expression, Command value) : base(expression, System.Dynamic.BindingRestrictions.Empty, value) { } public override System.Dynamic.DynamicMetaObject BindGetMember(System.Dynamic.GetMemberBinder binder) { var self = this.Expression; var bag = (Command)base.Value; Expression target; target = Expression.Call( Expression.Convert(self, typeof(Command)), typeof(Command).GetMethod("GetValue"), Expression.Constant(binder.Name) ); var restrictions = BindingRestrictions .GetInstanceRestriction(self, bag); return new DynamicMetaObject(target, restrictions); } #endregion } }

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• python tkinter gui

  - by Lewis Townsend

  I'm wanting to make a small python program for yearly temperatures. I can get nearly everything working in the standard console but I'm wanting to implement it into a GUI. The program opens a csv file reads it into lists, works out the average, and min & max temps. Then on closing the application will save a summary to a new text file. I am wanting the default start up screen to show All Years. When a button is clicked it just shows that year's data. Here is a what I want it to look like. Pretty simple layout with just the 5 buttons and the out puts for each. I can make up the buttons for the top fine with: Code: class App: def __init__(self, master): frame = Frame(master) frame.pack() self.hi_there = Button(frame, text="All Years", command=self.All) self.hi_there.pack(side=LEFT) self.hi_there = Button(frame, text="2011", command=self.Y1) self.hi_there.pack(side=LEFT) self.hi_there = Button(frame, text="2012", command=self.Y2) self.hi_there.pack(side=LEFT) self.hi_there = Button(frame, text="2013", command=self.Y3) self.hi_there.pack(side=LEFT) self.hi_there = Button(frame, text="Save & Exit", command=self.Exit) self.hi_there.pack(side=LEFT) I'm not sure as to how to make the other elements, such as the title & table. I was going to post the code of the small program but decided not to. Once I have the structure/framework I think I can populate the fields & I might learn better this way. Using Python 2.7.3

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• Validate if aTextBox Value Start with a Specific Letter

  - by Vincent Maverick Durano

  In case you will be working on a page that needs to validate the first character of the TextBox entered by a user then here are two options that you can use: Option 1: Using an array   1: <asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="server"> 2: <script type="text/javascript"> 3: function CheckFirstChar(o) { 4: var arr = ['A', 'B', 'C', 'D']; 5: if (o.value.length > 0) { 6: for (var i = 0; i < arr.length; i++) { 7: if (o.value.charAt(0) == arr[i]) { 8: alert('Valid'); 9: return true; 10: } 11: else { 12: alert('InValid'); 13: return false; 14: } 15: } 16: } 17: } 18: </script> 19: </asp:Content> 20: <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> 21: <asp:TextBox ID="TextBox1" runat="server" onblur="return CheckFirstChar(this);"></asp:TextBox> 22: </asp:Content>   The example above uses an array of string for storing the list of  characters that a TextBox value should start with. We then iterate to the array and compare the first character of TextBox value to see if it matches any characters from the array. Option 2: Using Regular Expression (Preferred way)   1: <asp:Content ID="Content1" ContentPlaceHolderID="HeadContent" runat="server"> 2: <script type="text/javascript"> 3: function CheckFirstChar(o) { 4: pattern = /^(A|B|C|D)/; 5: if (!pattern.test(o.value)) { 6: alert('InValid'); 7: return false; 8: } else { 9: alert('Valid'); 10: return true; 11: } 12: } 13: </script> 14: </asp:Content> 15: <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> 16: <asp:TextBox ID="TextBox1" runat="server" onblur="return CheckFirstChar(this);"></asp:TextBox> 17: </asp:Content>   The example above uses regular expression with the pattern  /^(A|B|C|D)/. This will check if the TextBox value starts with A,B,C or D. Please note that it's case sensitive. If you want to allow lower case then you can alter the patter to this /^(A|B|C|D)/i. The i in the last part will cause a case-insensitive search.   That's it! I hope someone find this post useful!

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• Converting PDF to PostScript with GhostScript

  - by Joel Martinez

  I installed ghostscript and updated the appropriate path variables ... however, I'm getting an error when I try to execute this command: C:\PROGRA~1\gs\gs8.64\lib>pdf2ps mydocument.pdf mydocument.ps Access is denied. Unable to open command line file _.at Is this the right command? did I miss some configuration or path setting? Otherwise, is there a sane method of doing this conversion? Thanks!

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