Exposing .NET events to COM?

Exposing .NET events to COM?

.NET events can be exposed to COM by using the ComSourceInterfaces attribute in C#. Here's how:

  • Declare a delegate: Declare a delegate for the event, like this:
public delegate void MyEventHandler(object sender, EventArgs e);
  • Declare the event: Declare the event using the delegate, like this:
public event MyEventHandler MyEvent;
  • Apply the ComSourceInterfaces attribute: Apply the ComSourceInterfaces attribute to the class that defines the event, like this:
[ComSourceInterfaces(typeof(IMyEvents))] public class MyClass { public delegate void MyEventHandler(object sender, EventArgs e); public event MyEventHandler MyEvent; // Other class members }

In this example, IMyEvents is the COM interface that defines the event. The ComSourceInterfaces attribute specifies that the class implements this interface, which makes the event visible to COM clients.

  • Implement the COM interface: Implement the IMyEvents interface to provide the COM client with the necessary event information, like this:
[Guid("12345678-1234-1234-1234-123456789ABC")] [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IMyEvents { [DispId(1)] void MyEvent(); }

In this example, 12345678-1234-1234-1234-123456789ABC is the GUID of the interface. The DispId attribute specifies the ID of the event method.

By following these steps, you can expose .NET events to COM clients. When a COM client subscribes to the event, the MyEventHandler delegate will be called, which will in turn raise the MyEvent event.

Examples

  1. "C# expose .NET events to COM"

    [ComVisible(true)] [ClassInterface(ClassInterfaceType.AutoDual)] public class MyClass { [ComVisible(true)] public delegate void MyEventHandler(string message); [ComVisible(true)] public event MyEventHandler OnMyEvent; [ComVisible(true)] public void TriggerEvent(string message) { OnMyEvent?.Invoke(message); } }

    Description: Demonstrates exposing a .NET event to COM using the ComVisible attribute and a custom delegate.

  2. ".NET events in COM interop"

    [ComVisible(true)] [ClassInterface(ClassInterfaceType.AutoDual)] public class MyEventProvider { [ComVisible(true)] public delegate void MyEventHandler(string message); [ComVisible(true)] public event MyEventHandler OnMyEvent; [ComVisible(true)] public void TriggerEvent(string message) { OnMyEvent?.Invoke(message); } }

    Description: Illustrates exposing a .NET event to COM with the ComVisible attribute and a custom delegate for interop scenarios.

  3. "C# COM interop expose .NET events"

    [ComVisible(true)] [ClassInterface(ClassInterfaceType.AutoDual)] public class EventProvider { [ComVisible(true)] public delegate void MyEventHandler(string message); [ComVisible(true)] public event MyEventHandler OnMyEvent; [ComVisible(true)] public void RaiseEvent(string message) { OnMyEvent?.Invoke(message); } }

    Description: Shows how to expose .NET events to COM interop using the ComVisible attribute and a custom delegate.

  4. "Expose .NET events to COM using ComVisible"

    [ComVisible(true)] [ClassInterface(ClassInterfaceType.AutoDual)] public class MyComClass { [ComVisible(true)] public delegate void MyEventHandler(string message); [ComVisible(true)] public event MyEventHandler OnMyEvent; [ComVisible(true)] public void TriggerEvent(string message) { OnMyEvent?.Invoke(message); } }

    Description: Demonstrates exposing a .NET event to COM by applying the ComVisible attribute to the class and event.

  5. "C# COM event handling"

    [ComVisible(true)] [ClassInterface(ClassInterfaceType.AutoDual)] public class EventProvider { [ComVisible(true)] public delegate void MyEventHandler(string message); [ComVisible(true)] public event MyEventHandler OnMyEvent; [ComVisible(true)] public void RaiseEvent(string message) { OnMyEvent?.Invoke(message); } }

    Description: Illustrates handling .NET events in a COM client by declaring a delegate and raising an event.

  6. "COM interop with .NET events example"

    [ComVisible(true)] [ClassInterface(ClassInterfaceType.AutoDual)] public class EventProvider { [ComVisible(true)] public delegate void MyEventHandler(string message); [ComVisible(true)] public event MyEventHandler OnMyEvent; [ComVisible(true)] public void RaiseEvent(string message) { OnMyEvent?.Invoke(message); } }

    Description: Shows an example of COM interop with .NET events by using ComVisible, a delegate, and event declaration.

  7. "C# COM event source"

    [ComVisible(true)] [ClassInterface(ClassInterfaceType.AutoDual)] public class MyEventSource { [ComVisible(true)] public delegate void MyEventHandler(string message); [ComVisible(true)] public event MyEventHandler OnMyEvent; [ComVisible(true)] public void RaiseEvent(string message) { OnMyEvent?.Invoke(message); } }

    Description: Demonstrates creating a COM event source in C# with a delegate and an event.

  8. ".NET COM event sink"

    [ComVisible(true)] [ClassInterface(ClassInterfaceType.AutoDual)] public class MyEventSink { [ComVisible(true)] public void OnMyEvent(string message) { // Event handling logic } }

    Description: Illustrates a .NET COM event sink that implements a method to handle the COM event.

  9. "C# COM event callback"

    [ComVisible(true)] [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IMyEventCallback { [DispId(1)] void OnMyEvent(string message); } [ComVisible(true)] [ClassInterface(ClassInterfaceType.None)] public class EventProvider { private IMyEventCallback callback; [ComVisible(true)] public void RegisterCallback(IMyEventCallback callback) { this.callback = callback; } [ComVisible(true)] public void RaiseEvent(string message) { callback?.OnMyEvent(message); } }

    Description: Shows a C# COM event callback scenario using an interface with IDispatch and a class implementing the callback registration and event raising.

  10. "C# COM event handler registration"

    [ComVisible(true)] [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)] public interface IMyEventCallback { [DispId(1)] void OnMyEvent(string message); } [ComVisible(true)] [ClassInterface(ClassInterfaceType.None)] public class EventProvider { private IMyEventCallback callback; [ComVisible(true)] public void RegisterCallback(IMyEventCallback callback) { this.callback = callback; } [ComVisible(true)] public void RaiseEvent(string message) { callback?.OnMyEvent(message); } }

    Description: Demonstrates registering a C# COM event handler by defining an interface with IDispatch and a class for callback registration and event raising.

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