Using reflection to specify the type of a delegate (to attach to an event)?

Question

What I effectively want to do is something like this (I realise this is not valid code):

// Attach the event.
try
{
    EventInfo e = mappings[name];
    (e.         


        

Answer 1

You can use Delegate.CreateDelegate to accomplish your goal like this:

public void RegisterHandler(string name)
{
    EventInfo e = mappings[name];
    EventHandler<AutoWrapEventArgs> handler = (s, raw) =>
        {
            func.Call(this, raw.GetParameters());
        };
    e.AddEventHandler(this, Delegate.CreateDelegate(e.EventHandlerType, null, handler.Method));
}

Answer 2

Bingo! The trick is to get a reference to the constructor for the delegate type and then invoke it using the following parameters:

• The target object of the delegate (backend.Target)
• The delegate's pointer (backend.Method.MethodHandle.GetFunctionPointer())

The actual code that does this looks like (t in this case is the generic argument provided to EventHandler<> during inheritance):

Type t = e.EventHandler.GetGenericArguments()[0];
Delegate handler = (Delegate)
    typeof(EventHandler<>)
    .MakeGenericType(t)
    .GetConstructors()[0]
    .Invoke(new object[]
        {
            backend.Target,
            backend.Method.MethodHandle.GetFunctionPointer()
        });

You can then use the delegate for the event adding like so:

e.AddEventHandler(this, handler);