How to sink COM events from Silverlight?

I want to raise an event from a .NET class, and receive this event in Silverlight code (out-of-browser, using the COM interop support added in SL4).

Can anyone point out the problem in my code? Do I maybe need to do more attribute-decorated interface boilerplate to get this working?

Code:

Rather than write native COM code, I am writing .NET code and exposing it via COM interop.

My event-raising .NET class looks like this:

using System;

namespace TestComInterop2 {
  public class TestClass {
    public event EventHandler TestEvent;
    public void Fire() {
      if (TestEvent != null)
        TestEvent(this, EventArgs.Empty);
    }
  }
}

My SL4 client code looks like this:

...

private delegate void HandlerDelegate(dynamic sender, dynamic eventArgs);

private void TestEventSinking(object sender, RoutedEventArgs e)
{
  // Create instance of COM-registered .NET class
  var testClass = AutomationFactory.CreateObject("TestComInterop2.TestClass");

  // Subscribe to event (second line fails with System.Exception)
  //
  //    "Failed to add event handler. Possible reasons include: the object does not
  //    support this or any events, or something failed while adding the event."
  //
  AutomationEve开发者_C百科nt testEvent = AutomationFactory.GetEvent(testClass, "TestEvent");
  testEvent.AddEventHandler(new HandlerDelegate(HandleTestEvent));

  // Fire the event
  testClass.Fire();
}

private void HandleTestEvent(object sender, object eventargs)
{
  MessageBox.Show("Event fired");
}

...

Use the [ComSourceInterface] attribute on your class. The relevant MSDN Library topic is here.