Forwarding/relaying .NET events

Question

My class has an event which external objects will subscribe to:

public event EventHandler<MessageReceivedEventArgs> MessageReceived;

However, an internal Listener object, running on it's own thread, will actually be originating the event.

private class Listener
{
    public void Run()
    {
         // events raised here which should be forwarded
         // to parent's MessageReceived
    }
};

My inclination is to create an event with the same signature on the Listener, and subscribe to it in the main class in order to raise it on MessageReceived. This seems a little cumbersome, so I was wondering if there is a neat/idiomatic way of forwarding events like this.

Answer 1

You can use event add/remove accessors so that events wired to the external-facing event are "forwarded" to the internal listener

public event EventHandler<MessageReceivedEventArgs> MessageReceived {
   add { this.listener.MessageRecieved += value; }
   remove { this.listener.MessageRecieved -= value; }
}

This means you need to create an event in the listener, but the benefit is that there is no other plumbing to wire up the event.

Answer 2

You could do that with an event, or you could create a method in your main class called ReceiveMessage() and call that from the listener (and then raise the event from there).