Forwarding events in C#

Question

I\'m using a class that forwards events in C#. I was wondering if there\'s a way of doing it that requires less code overhead.

Here\'s an example of what I have so f

Answer 1

IMO, your original code is (more or less) correct. In particular, it allows you to provide the correct sender (which should be the B instance for people who think they are subscribing to an event on B).

There are some tricks to reduce the overheads at runtime if the event isn't subscribed, but this adds more code:

class B {
   A m_A = new A();
   private EventType eventB;
   public event EventType EventB {
       add { // only subscribe when we have a subscriber ourselves
           bool first = eventB == null;
           eventB += value;
           if(first && eventB != null) m_A.EventA += OnEventB;
       }
       remove { // unsubscribe if we have no more subscribers
           eventB -= value;
           if(eventB == null) m_A.EventA -= OnEventB;
       }
   }

   protected void OnEventB(object sender, EventArgsType args) {
      eventB?.Invoke(this, args); // note "this", not "sender"

   }
}

Answer 2

Absolutely:

class B
{
    private A m_a = new A();

    public event EventType EventB
    {
        add { m_a.EventA += value; }
        remove { m_a.EventA -= value; }
    }
}

In other words, the EventB subscription/unsubscription code just passes the subscription/unsubscription requests on to EventA.

Note that this doesn't allow you to raise the event just for subscribers who subscribed to EventB, however. It's like passing someone's address directly onto a mass marketing company, whereas your original way is more like subscribing to the mass marketing company yourself, and allowing people to ask you to send copies of the mails to them.