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• Should I use the Model-View-ViewModel (MVVM) pattern in Silverlight projects?

  - by Jon Galloway

  One challenge with Silverlight controls is that when properties are bound to code, they're no longer really editable in Blend. For example, if you've got a ListView that's populated from a data feed, there are no elements visible when you edit the control in Blend. I've heard that the MVVM pattern, originated by the WPF development community, can also help with keeping Silverlight controls "blendable". I'm still wrapping my head around it, but here are some explanations: http://www.nikhilk.net/Silverlight-ViewModel-Pattern.aspx http://mark-dot-net.blogspot.com/2008/11/model-view-view-model-mvvm-in.html http://www.ryankeeter.com/silverlight/silverlight-mvvm-pt-1-hello-world-style/ http://jonas.follesoe.no/YouCardRevisitedImplementingTheViewModelPattern.aspx One potential downside is that the pattern requires additional classes, although not necessarily more code (as shown by the second link above). Thoughts?

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• Best way to provide software settings?

  - by claws

  I'm using C# .NET. In my software I'm providing settings dialog through which user can set the application settings which I want to save to a file. Requirements (typical): Every class I defined uses some part of these settings. So, these should be global to all classes. These should be loaded while software is started. When ever user changes settings and clicks 'save'/'apply'. Current settings should change. I am wondering what is the best way to do this? Also, what is the best way to save these settings to disk? I mean should I create a Settings class object and serializing it to 'settings.dat' or provide an structured file like XML/JSON

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• Scala model-view-presenter, traits

  - by Ralph

  I am a fan of Martin Fowler's (deprecated) model-view-presenter pattern. I am writing a Scala view class containing several button classes. I would like to include methods to set the action properties of the buttons, to be called by the presenter. A typical code fragment looks like this: private val aButton = new JButton def setAButtonAction(action: Action): Unit = { aButton.setAction(action) } This code is repeated for each button. If Java/Scala had the C preprocessor, I would create a macro to generate this code, given the button name (no lectures on the evils of the C preprocessor, please). This code is obviously very verbose and repetitive. Is there any better way way to do this in Scala, perhaps using traits? Please hold the lectures about scala.swing. I looking for a general pattern here.

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• What is the worst class/variable/function name you have ever encountered

  - by Chris Noe

  Naming things well is arguably Job 1 for professional programmers. Yet we have all suffered from some bad naming choices from time to time. So just to vent a little, what are some doozies that you may have run across? Just to get things started: One of our original developers wasn't sure what to call a secondary key - on what turned out to be a primary table for this app - so he called it: DL2WhateverTheHellThatIs. Unfortunately this system generates entity mappings from the XML, and attributes defined there result in classes, methods, and constants that are referenced through-out the app. To this day it is very hard to find a source file that does not reference this, er, thing! A few actual examples: DL2WhateverTheHellThatIsBean cos = (DL2WhateverTheHellThatIsBean)itr.next(); String code = getDL2WhateverTheHellThatIs().getCode(); From from = new From("DL2WhateverTheHellThatIs"); String filter = "_dL2WhateverTheHellThatIs._code"; (Very difficult to refactor)

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• Mixing table per subclass and per hierarchy in hibernate

  - by Xelluloid

  In my database there are two three tables. The first one, table ABSTRACT, holds three columns id, type, someText This table contains all abstract information for the abstract class abstract. Now the two tables CONCRETEONE and CONCRETETWO contain all information for the concrete classes concreteOne and concreteTwo. Now I know I could use the table per subclass strategy from hibernate to create a mapping with inheritance. But as I have a column that marks the type of the concrete implementation could it be possible to create some mixed behaviour like a table per subclass strategy with an discriminator?

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• I need help translating this portion of the ECMAScript grammar?

  - by ChaosPandion

  I've been working on my own implementation of ECMAScript for quite some time now. I have basically done everything by hand to help gain a deep understanding of the process. Repeated attempts to analyze and understand this portion of the grammar have failed so I've been working on the run time instead. Now I am at a point were I will be working on object literals so I really need to polish my syntactic analyzer. Can anyone put this in terms a language parser novice could understand? My biggest source of confusion is the following: new MemberExpression Arguments This is supposed to be a member expression, but this seemingly conflicts with the following: NewExpression : MemberExpression new NewExpression Is a new expression a member expression or a left hand side expression? To be honest I am having trouble laying out the proper C# classes for the concrete grammar. MemberExpression : PrimaryExpression FunctionExpression MemberExpression [ Expression ] MemberExpression . IdentifierName new MemberExpression Arguments NewExpression : MemberExpression new NewExpression CallExpression : MemberExpression Arguments CallExpression Arguments CallExpression [ Expression ] CallExpression . IdentifierName LeftHandSideExpression : NewExpression CallExpression

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• Deleting from arraylist and exporting back to .buab file(Java)

  - by Dave

  Ive made an address book. I can currently write to the arraylist and save it back to the .buab file, but I cant delete from the arraylist and export it back to the .buab file? Im pretty much stuck on this. Im able to retrive contacts from the .buab and scroll through them using the JTextFields and buttons ive created. Any help will be dearly appreciated. Ive set up seprate classes for all operations (newcontacts, nextcontact etc). If you need the code posted let me know.. Cheers Dave

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• Should I use implicit conversions to enforce preconditions?

  - by Malvolio

  It occurs to me that I could use use implicit conversions to both announce and enforce preconditions. Consider this: object NonNegativeDouble { implicit def int2nnd(d : Double) : NonNegativeDouble = new NonNegativeDouble(d) implicit def nnd2int(d : NonNegativeDouble) : Double = d.v def sqrt(n : NonNegativeDouble) : NonNegativeDouble = scala.math.sqrt(n) } class NonNegativeDouble(val v : Double ) { if (v < 0) { throw new IllegalArgumentException("negative value") } } object Test { def t1 = { val d : Double = NonNegativeDouble.sqrt(3.0); printf("%f\n", d); val n : Double = NonNegativeDouble.sqrt(-3.0); } } Ignore for the moment the actual vacuity of the example: my point is, the subclass NonNegativeDouble expresses the notion that a function only takes a subset of the entire range of the class's values. First is this: A good idea, a bad idea, or an obvious idea everybody else already knows about Second, this would be most useful with basic types, like Int and String. Those classes are final, of course, so is there a good way to not only use the restricted type in functions (that's what the second implicit is for) but also delegate to all methods on the underlying value (short of hand-implementing every delegation)?

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• Problems with listening for an event in child object in Actionscript

  - by Raigomaru

  I have two classes. The first one (the starting class): package { import flash.display.Sprite; import flash.events.KeyboardEvent; import tetris.*; public class TetrisGame extends Sprite { private var _gameWell:Well; public function TetrisGame() { _gameWell = new Well(); addChild(_gameWell); } } } The second: package tetris { import flash.display.Sprite; import flash.events.KeyboardEvent; public class Well extends Sprite { public function Well() { super(); addEventListener(KeyboardEvent.KEY_DOWN, onKeyboard); } private function onKeyboard(event:KeyboardEvent):void { //some code is here } } } But when I press any buttons on my keyboard, the child class Well doesn't have any reaction. What's the problem?

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• design using a readonly class in c#

  - by edosoft

  Hi Small design question here. I'm trying to develop a calculation app in C#. I have a class, let's call it InputRecord, which holds 100s of fields (multi dimensional arrays) This InputRecordclass will be used in a number of CalculationEngines. Each CalculcationEngine can make changes to a number of fields in the InputRecord. These changes are steps needed for it's calculation. Now I don't want the local changes made to the InputRecord to be used in other CalculcationEngine's classes. The first solution that comes to mind is using a struct: these are value types. However I'd like to use inheritance: each CalculationEngine needs a few fields only relevant to that engine: it's has it's own InputRecord, based on BaseInputRecord. Can anyone point me to a design that will help me accomplish this?

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• Creating a provider. I receive this exception java.lang.SecurityException

  - by user308806

  Hello, I'm trying to create a provider. when I run the code i receive this exception Exception in thread "main" java.lang.SecurityException: JCE cannot authenticate the provider MyProvider at javax.crypto.Cipher.getInstance(DashoA13*..) at javax.crypto.Cipher.getInstance(DashoA13*..) at hellman.Main.main(Main.java:68) Caused by: java.util.jar.JarException: Cannot parse file:/C:/Documents%20and%20Settings/brahim%20%20chami/Bureau/Project%233/hellman/build/classes/ at javax.crypto.SunJCE_c.a(DashoA13*..) at javax.crypto.SunJCE_b.b(DashoA13*..) at javax.crypto.SunJCE_b.a(DashoA13*..) ... 3 more Java Result: 1

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• Update JProgressBar from new Thread

  - by Dacto

  How can I update the JProgressBar.setValue(int) from another thread? My secondary goal is do it in the least amount of classes possible. Here is the code I have right now: **Part of the main class....** pp.addActionListener( new ActionListener(){ public void actionPerformed(ActionEvent event) { new Thread(new Task(sd.getValue())).start(); } }); public class Task implements Runnable{ int val; public Task(int value){ this.val = value; } @Override public void run() { for (int i=0; i<=value; i++){ //Progressively increment variable i pbar.setValue(i); //Set value pbar.repaint(); //Refresh graphics try{Thread.sleep(50);} //Sleep 50 milliseconds catch (InterruptedException err){} } } } pp is a JButton and starts the new thread when the JButton is clicked. pbar is the JProgressBar object from the Main class. How can I update its value?(progress) The code above in run() cannot see the pbar.

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• Do controls need to be defined in a web app or will .NET do it for you

  - by Chris

  I always thought that when you dropped a control onto an .aspx page that a declaration of that control ended up being generated for you (either in a designer file, or within your code behind). All of the apps I have worked on have worked this way. A coworker of mine was installing resharper and it was showing that all her code behind pages would not build. Turned out that resharper could not find a definition for any control that she has dropped onto her markup. She has no designer files, and no declarations in markup. Do they get automatically built when putting together the partial classes? Is there an option at that page/project level to instruct .NET to do this for you? Is this a difference between web app and web site? This is a a .NET 3.5 site, C#, and it is running in a production environment. Thanks in advance

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• Recommended Python publish/subscribe/dispatch module ?

  - by Eli Bendersky

  From PyPubSub: Pypubsub provides a simple way for your Python application to decouple its components: parts of your application can publish messages (with or without data) and other parts can subscribe/receive them. This allows message "senders" and message "listeners" to be unaware of each other: one doesn't need to import the other a sender doesn't need to know "who" gets the messages, what the listeners will do with the data, or even if any listener will get the message data. similarly, listeners don't need to worry about where messages come from. This is a great tool for implementing a Model-View-Controller architecture or any similar architecture that promotes decoupling of its components. There seem to be quite a few Python modules for publishing/subscribing floating around the web, from PyPubSub, to PyDispatcher to simple "home-cooked" classes. Can you recommend a module that works well in most cases ? Which modules have you had positive experience with ? Negative ? Thanks in advance

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• What are the pros/cons to these 2 ways of defining parameters for a web service method

  - by Antony Scott

  I have an existing web service I need to expand, but it has not gone into production yet. So, I am free to change the contracts as I see fit. But I am not sure of the best way to define the methods. I am leaning towards Method 2 for no other reason than I cannot think of good names to give the parameters classes! Are there any major disadvantages to using Method 2 over Method 1? Method 1 [DataContract(Namespace = Constants.ServiceNamespace)] public class MyParameters { [DataMember(Order = 1, IsRequired = true)] public int CompanyID { get; set; } [DataMember(Order = 2, IsRequired = true)] public string Filter { get; set; } } [ServiceContract(Namespace = Constants.ServiceNamespace)] public interface IMyService { [OperationContract, FaultContract(MyServiceFault)] MyResult MyMethod(MyParameters params); } Method 2 public interface IMyService { [OperationContract, FaultContract(MyServiceFault)] MyResult MyMethod(int companyID, string filter); }

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• Jar extraction and verification in BlackBerry

  - by Basilio

  Hi All, The application I am currently working on requires me to extract contents from and verify the authenticity of the signed jar that is stored on the SD Card. In Java [and Android], we have the java.util.jar and java.util.zip classes, that allow to extract jar. However, J2ME or BlackBerry® does not provide support for these packages. I have, however, successfully extracted these using the third party ZipMe library. Can anyone let me know, how to get the signature block from the .DSA/.RSA file to authenticate the jar? I have the certificate that was used to sign the jar as well. This is easily done in Java using the getCertificates() method available in java.util.jar.JarFile. Is there any 3rd party API available that emulates the JarFile for BlackBerry®? Any help in this regard will be deeply appreciated. Thanks & Regards Basilio John Vincent D'souza

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• Declare 2 types inside using statement gives compile error?

  - by citronas

  I want to use this line of code: using (ADataContext _dc = new ADataContext(ConnectionString), BDataContext _dc2 = new BrDataContext(ConnectionString)){ // ...} This gives a compile error: Cannot use more than one type in a for, using, fixed or declartion statement. I thought this was possible? MSDN says it is: http://msdn.microsoft.com/en-us/library/yh598w02%28VS.80%29.aspx In the MSDN sample code Font is used, which is class and thereby a reference type as well as my two DataContext classes. What went wrong here? How does my attempt differ from the MSDN sample?

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• Having a base class function depend on its child class C#

  - by Junk Junk

  I have a Base class with a method that a child class will almost always override. However, instead of replacing the base class' method entirely, I would like for whatever is derived in the child class to be added to what is already in the base class. For Example: class BaseClass public string str() { var string = "Hello my name is" ; } class ChildClass : BaseClass public override string str(){ var string = "Sam"; } The point is that if I want to access the str() method by creating an instance of the ChildClass, the string will print out as "Hello, my name is Sam". I've been looking around and all I have been finding is that this should NOT happen, as the base class shouldn't even know that it is being inherited. So, if the design is false, how would I go about doing this? Keep in mind that there will be multiple child classes inheriting from BaseClass. Thank you

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• How to recognize the touch of a non regular sprite image ?

  - by srikanth rongali

  I have a sprite and if it is touched the touch should be recognized. I used the coordinates to do so. I took the coordinates (min x, min y, max x , max y)of the sprite image. But The sprite image is not a rectangular shape. So, even if I touch the coordinates outside the sprite and inside the rectangular bounds the sprite is recognized. But for my application I need only the sprite to be recognized. So, I have to take only the coordinates of the sprite, but it is not regular shape. I am using CCSprite in my program. So, what can I do to for only the sprite to be selected ? Which classes should use for this? Thank You.

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• VB.NET template instance - passing a variable data type

  - by FerretallicA

  As the title suggests, I'm tyring to pass a variable data type to a template class. Something like this: frmExample = New LookupForm(Of Models.MyClass) 'Works fine Dim SelectedType As Type = InstanceOfMyClass.GetType() 'Works fine repoGeneric = New Repositories.Repository(Of SelectedType) 'Ba-bow! repoGeneric = New Repositories.Repository(Of InstanceOfMyClass.GetType()) 'Ba-bow! I'm assuming it's something to do with the template being processed at compile time but even if I'm off the mark there, it wouldn't solve my problem anyway. I can't find any relevant information on using Reflection to instance template classes either. (How) can I create an instance of a dynamically typed repository at runtime?

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• Should i use HttpResponse.End() for a fast webapp?

  - by acidzombie24

  HttpResponse.End() seems to throw an exception according to msdn. Right now i have the choice of returning a value to say end thread (it only goes 2 functions deep) or i can call end(). I know that throwing exceptions is significantly slower (read the comment for a C#/.NET test) so if i want a fast webapp should i consider not calling it when it is trivially easy to not call it? -edit- I do have a function call in certain functions and in the constructor in classes to ensure the user is logged in. So i call HttpResponse.End() in enough places although hopefully in regular site usage it doesn't occur too often.

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• what is the exact difference between PHP static class and singleton class

  - by Saif Bechan

  I have always used a Singleton class for a registry object in PHP. As all Singleton classes I think the main method looks like this: class registry { public static function singleton() { if( !isset( self::$instance ) ) { self::$instance = new registry(); } return self::$instance; } public function doSomething() { echo 'something'; } } So whenever I need something of the registry class I use a function like this: registry::singleton()->doSomethine(); Now I do not understand what the difference is between creating just a normal static function. Will it create a new object if I just use a normal static class. class registry { public static function doSomething() { echo 'something'; } } Now I can just use: registry::doSomethine(); Can someone explain to me what the function is of the singleton class. I really do not understand this.

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• C# compile finalize method's on runtime?

  - by Royi Namir

  As im reading through 3 books about GC , ive notice some strange fact : C# via CLR CriticalFinalizerObject : the CLR treats this class and classes derived from it in a very special manner what ??? "not find enough memory to COMPILE a method? " IMHO - the code should be already compiled... no ? when Im writing c# code - the whole code is compiled to IL before its running... no? but according to the text - at RUNTIME - he MAY find insufficient memory for compile... Help ?

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• Deserialization on client side in Domain Service

  - by ankit

  I have 2 classes: Person and Contact. Person class has a property named ContactNumber which returns the Contact type, and this property is marked as a DataMember for serialization. I have marked Contact type as a DataContract. On the client side I am able to get the values, but when I try to insert a value and then do submit, I get the following exception: Failed to deserialize change-set. Failed to convert value of type 'Dictionary`2' to type 'Contact' Stack Trace is: at System.Web.Ria.DataServiceSubmitRequest.GetChangeSet(DomainService domainService) at System.Web.Ria.DataServiceSubmitRequest.Invoke(DomainService domainService) at System.Web.Ria.DataService.System.Web.IHttpHandler.ProcessRequest(HttpContext context) Can anyone give me the solution ?

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• Maximizing the number of threads to fully utilize all available resources without hindering overall

  - by Matt

  Let's say I have to generate a bunch of result files, and I want to make it as fast as possible. Each result file is generated independently of any other result file; in fact, one could say that each result file is agnostic to every other result file. The resources used to generate each result file is also unique to each. How can I dynamically decide the optimal number of threads to run simultaneously in order to minimize the overall run time? Is my only option to write my own thread manager that watches performance counters and adjust accordingly or does there exists some solid classes that already accomplish this?

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