C# removing an event handler

Question

I've been doing this for a while, but I haven't noticed that I've been using a new each time I remove an event handler. Am I supposed to be creating a new object?

Basically is there a difference between 1 and 2?

1. ethernetdevice.PcapOnPacketArrival -= new SharpPcap.PacketArrivalEvent(ArrivalResponseHandler);

2. ethernetdevice.PcapOnPacketArrival -= ArrivalResponseHandler;

EDIT: Okay this is a duplicate. Sorry about that. Answer posted here.

Two delegates of the same type with the same targets, methods, and invocation lists are considered equal.

Solution 1

There is no difference between 1 and 2, because 2 is syntactic sugar for 1. Only if 2 referred to a class-level delegate instance field rather than the actual method name would there be a difference in the compiled IL.

In terms of what happens at runtime, the event Remove method does not seem to care whether or not the delegate instance passed to it is the same one as the one passed to the Add method. I can't remember off-hand why this is, but I would guess that delegate instances are always interned.

EDIT: Jon Skeet says that the event Remove method uses value equality (Delegate.Equals) to determine which delegate to remove from the list, rather than interning + reference equality. Same end result, different method. :-)

Solution 2

The second version is equivalent to the first; it just uses a shorter syntax. This was implemented in C# 2.0