Delegate Gotcha
07.11.06Filed Under: Uncategorized
A while back i was trying to find a solution to the delegate gotcha and stumbled upon, even more recently, some answers to a lot of my questions… they trackback and link with each other at some point, but my entry point to this discussion was mostly through, in no specific order:
Observable property pattern, memory leaks and weak delegates for .Net. - Alexey A. Popov
Simulating “Weak Delegates” in the CLR - Greg Schechter
.Net 2.0 Generics, Anonymous Methods, and Delegate inference bug - Udi Dahan
After reviewing a lot of the different solutions, i’m currently experimenting with an idea. Given your usual suspect:
public class EventSource
{
public event EventHandler FireEvent;
public void OnFireEvent( )
{
if(null != FireEvent)
FireEvent( this, EventArgs.Empty );
}
}
I’ve reworked some ideas and using WeakReference, rewritten the EventSource above as follows:
public class EventSource
{
private Dictionary<EventHandler, WeakReference> origDelgs =
new Dictionary<EventHandler, WeakReference>();
public event EventHandler FireEvent
{
add
{
if( !origDelgs.ContainsKey( value ) )
origDelgs.Add( value, new WeakReference( value ) );
}
remove
{
if( origDelgs.ContainsKey( value ) )
origDelgs.Remove( value );
}
}
public void OnFireEvent( )
{
foreach( WeakReference aref in origDelgs.Values )
{
if( null != aref.Target )
{
EventHandler hdl = (EventHandler)aref.Target;
hdl.Invoke( this, EventArgs.Empty );
}
}
}
}
Now, at least, if my sink goes out of scope, it won’t get resurrected 
Will continue experimenting with this idea and see how it performs….
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