COM+ events with c# and .NET

Question

I'm trying to get access to certain parts of my application through COM, mainly because I need a Delphi application to be able to invoke certain services on the .NET application.

I've managed to expose some methods via COM inheriting from ServicedComponent class and its working fine.

Now I need to be able to raise events to the client so I can alert him when certain things occur. I currently have something like this:

public interface IEvents
{
  void OnMessage();
}

[EventClass]    
[ComVisible(true)]
public class MyEventsClass : ServicedComponent, IEvents
{
  public void OnMessage()
  {
  }
}

but when I import the TypeLibrary from Delphi I get this:

IEvents = interface(IDispatch)
    ['{E7605303-F968-3509-829B-BF70084053C4}']
    procedure OnMessage; safecall;
  end;

IEventsDisp = dispinterface
    ['{E7605303-F968-3509-829B-BF70084053C4}']
    procedure OnMessage; dispid 1610743808;
  end;

which I don't really know how to use. I was expecting an IUnknown interface that I can implement and provide to the service through a MyService.Register(IEvents events)...

I think I'm completely lost here... Any advice or reference about how to properly implement COM+ events with .NET?

Answer 1

I'm still unsure of what exactly is the use for EventClass by I've discovered you don't need to use it. I simply have declared this:

[ComVisible(true)]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IMyEventIface
{
}

And with that the interface is exported as an IUnknown interface to Delphi.

Then you define a method on your ServicedComponent class which a connect signature like this:

public void Connect(IMyEventIface eventHandler)
{
  mEvents.Add(eventHandler);
}

which left you to manually handle the invoke of each client event handler but is the only way I've found.