Raise COM Event within C#

[califax2k]

Hi all, I am currently trying to send a COM Event from a .NET Assembly to another application. Therefore I am applying the approach that's found multiple times across the internet. Here it's outlined for short.

\[ComVisible(false)\]
public delegate void OnNotifyDelegate();

\[InterfaceType(ComInterfaceType.InterfaceIsIDispatch)\]
public interface Events
{
    void OnNotify();
}

\[Guid(EventSource.ClsID)\]
\[ClassInterface(ClassInterfaceType.None)\]
\[ComSourceInterfaces(typeof(Events))\]
public class EventSource : ServicedComponent, EventInterface
{
    private const string ClsID = "4A235195-E8B3-473b-8F14-F7F0ADFC40E0";
    
    public event OnNotifyDelegate OnNotify;

    public EventSource() { }

    public void CauseOnNotify()
    {
        OnNotify();
    }
}

Now, to raise the OnNotify Event I created a small WPF Application with a button, whose Click handler invokes the method CauseOnNotify above. I don't show it here, because that would be verbose. What I get is a NullPointerException because OnNotify is at the time it's invoked null. My question is: None of the examples mentions a instanciation of the delegate (which is why its null, but under which circumstances does this exception not happen? Where is the instance coming from? thanks in advance Lars

#pragma error( disable : * )

[Bernhard Hiller]

When some other object has registered for the event? I haven't tested with COM, but it looks similar to raising a "normal" .NET event:

if (this.MyEvent != null)
{
this.MyEvent(this, new EventArgs());
}

Only after an object has registered for MyEvent, it is different from null.