Question

If I have a type that inherits from EventArgs (lets call it EventArgs1), and a further bunch of classes that inherit from EventArgs1 (lets call them collectively EventArgsX), and then a bunch of events that are are of the type EventHandler<EventArgsX>, if at runtime I am passed the EventInfo for one of these events and I want to add an event handler that expects a second argument of type EventArgs1 (e.g. MyEventHandler(object sender, EventArgs1 e)) how would I do it?

If the event was of type EventHandler<EventArgs1> then I would just do this:

eventInfo.AddEventHandler(this, new EventHandler<EventArgs1>(MyEventHandler));

But this throws an exception when the event is of type EventHandler<EventArgsX>, and since I don’t know what EventArgsX is at compile time I can’t simply new up an EventHandler<EventArgsX> If I did know which event I was adding the handler to at compile time then this would be entirely acceptable:

MyEvent += MyEventHandler

But I simply can’t work out how to do this at runtime. Any suggestions?

Answer 1

I can’t simply new up an EventHandler<EventArgsX>

Sure you can, although you need to do it using Delegate.CreateDelegate() and reflection. Assuming MyEventHandler is an instance method on this, you could do it like this:

var eventInfo = …;

EventHandler<EventArgs1> badHandler = MyEventHandler;

var goodHandler = Delegate.CreateDelegate(
    eventInfo.EventHandlerType, this, badHandler.Method);

eventInfo.AddEventHandler(this, goodHandler);