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POSubscribe weakly to events obtained by reflection
 

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    <p>I'm making a <code>MessageBox</code> control in WPF using the MVVM pattern. This <code>MessageBox</code> will be used in multiple applications with different appearances, so ideally I want to keep code out of code-behind.</p> <p>I'm trying to make the <code>MessageBox</code> appear when an event is raised, specified in the declaration of the <code>MessageBox</code>.</p> <p>For example, this would be specified in the XAML of the window in which the <code>MessageBox</code> should appear.</p> <pre><code>&lt;dialog:MessageBox ShowOnEvent="EventRaised" EventContext="{Binding}" Message="I am a message box" IconType="Warning" ButtonsType="YesNo" /&gt; </code></pre> <p>The way this currently works: in the <code>MessageBox</code> ViewModel I'm using reflection to get the <code>EventInfo</code> for the event, then subscribing directly:</p> <pre><code>if (eventContext != null &amp;&amp; showOnEvent != string.Empty) { EventInfo eventInfo = eventContext.GetType ().GetEvent (showOnEvent); if (eventInfo != null) { eventInfo.AddEventHandler (eventContext, eventHandler); } else { Debug.WriteLine (string.Format ("Dialog: Couldn't find event {0} on {1}, check event name.", showOnEvent, eventContext)); } } </code></pre> <p>This shows the <code>MessageBox</code> when the event is raised, as expected.</p> <p><strong>However</strong>, the event handler means that the <code>MessageBox</code> ViewModel is not GC'd when the main window's View is disposed. This means that if another view for the main window is created, another <code>MessageBox</code> is created, so if the event is raised, both <code>MessageBox</code>s will show.</p> <p>I tried getting around this by using a <code>WeakEventManager</code>, but the <a href="http://msdn.microsoft.com/en-us/library/aa970850.aspx" rel="nofollow">Weak Event Patterns documentation</a> specify that an implementation of <code>WeakEventManager</code> should only handle one event - which means that I can't make a <code>ShowOnEventEventManager</code> with the event name as a string property and subscribe using that.</p> <p>Does anyone have any ideas for the best way to go about this?</p>
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    1. COIs that control supposed to be an overlay, or does it bring up a `MessageBox`?
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    2. CO@Will: It's an overlay - the basic `MessageBox` is not really flexible enough for my needs.
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    3. COSince you're subscribing to an event on the View, why not [subscribe to another event](http://msdn.microsoft.com/en-us/library/system.windows.frameworkelement.unloaded.aspx) as well, which will tell you when its time to unsubscribe to both?
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