Home/ Questions/Q 124539
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-11T05:00:59+00:00

recently I have been encountering problems with exposing events from .NET to COM. I

  • 0

recently I have been encountering problems with exposing events from .NET to COM.

I have been successful with this example (conceptually taken from http://blogs.msdn.com/andreww/archive/2008/10/13/exposing-events-from-managed-add-in-objects.aspx):

// The delegate type for our custom event.

[ComVisible(false)] public delegate void SomeEventHandler(object sender, EventArgs e);  // Outgoing (source/event) interface. [ComVisible(true)] [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IAddInEvents {     [DispId(1)]     void SomeEvent(object sender, EventArgs e); }  [ComVisible(true)] [ClassInterface(ClassInterfaceType.None)] [ComSourceInterfaces(typeof(IAddInEvents))] public class AddInUtilities : {            // Event field. This is what a COM client will hook up     // their sink to.     public event SomeEventHandler SomeEvent;      inernal void FireEvent(object sender, EventArgs e)     {         if (SomeEvent != null)         {             SomeEvent(sender, e);         }     } }

This works fine, because the IAddInEvents interface is defined as IDispatch. However, I need to publish an event source interface which is IUnknown. I do not have control over the event interface as it comes from a third-party library (which will also be the consumer of the published events). Whenever I try to hook to the events, VB environment (where I am trying to sink the events) crashes, so does the VBA environment which the third-party product (ESRI ArcMap) uses.

I have been able to (partially) implement IConnectionPointContainer interface (which COM uses in the background to handle events) manually, then I am able to sink the event and step into my IConnectionPointContainer implementation. However, this seems like an overkill to me and I think that there must an implicit support for this in .NET. Second, with this approach I instantly lose the delegate support.

Does anyone have any experience with this? Thanks in advance.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Ok, so I have been able to this by implementing the classic COM IConnectionPointCointainer, IConnectionPoint and IConnection (plus the enumeration interfaces). It does not integrate into the .NET delegate/event model, but works.

    • 0