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POQuestion About Passing Parameters To Methods That Return Lambdas
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  1. POQuestion About Passing Parameters To Methods That Return Lambdas
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    copied!<p>(with C# 3.0 and VS 2008).</p> <p>Doing MVVM WPF stuff you often write properties like this:</p> <pre><code>public bool MyProperty { get{return _myProperty;} set{ if(_myProperty == value)return; _myProperty = value; RaisePropertyChanged("MyProperty"); } } </code></pre> <p>Doing TDD I often end up writing tests such as:</p> <pre><code>[Test] public void MyPropertyRaisesPropertyChangedWhenChanged(){ var mySUT = CreateSUT(); bool eventRaised = false; string propName = ""; mySUT.PropertyChanged += (s,e)=&gt;{eventRaised = true;propName = e.PropertyName;}; Assert.That(mySUT.MyProperty,Is.False(),"mySUT.MyProperty"); mySUT.MyProperty = true; Assert.That(eventRaised,"eventRaised"); Assert.That(propName, Is.EqualTo("MyProperty"),"propName"); // could check not raised when set same... } </code></pre> <p>I experimented with a method like this:</p> <pre><code>public class MyTestMethods{ public static PropertyChangedEventHandler MakePropertyChangedHandler( bool eventWasRaised, string propertyName){ return (s,e)=&gt;{eventWasRaised = true; propertyName = e.PropertyName}; } } </code></pre> <p>So that I could write my test:</p> <pre><code>[Test] public void MyPropertyRaisesPropertyChangedWhenChanged(){ var mySUT = CreateSUT(); bool eventRaised = false; string propName = ""; mySUT.PropertyChanged += MyTestMethods.MakePropertyChangedHandler(eventRaised,propName); // etc... } </code></pre> <p>But VS2008 told me that eventRaised would always be false.</p> <p>I thought maybe changing MakePropertyChangedHandler to use ref parameters would work</p> <pre><code> public static PropertyChangedEventHandler MakePropertyChangedHandler( ref bool eventWasRaised, ref string propertyName){ return // lambda... } </code></pre> <p>but VisualStudio tells me 'Cannot use ref or out parameter 'x' inside an anonymous method body'.</p> <p>Can anyone tell me if it's possible to write a working method like MakePropertyChangedHandler and if not, how come?</p>
 

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