Question

Throwing an exception is costly in terms of writing good performance code. But what about raising an event? Hence this theoretical querstion to the .net clr crowd:

What are the memory implications concerning raising an event with one subscriber? With 1 000 000 subscribers? How to calculate these implications? Does raising one event euqal calling a member method of (the otherwise handler) subscriber directly?

Answer 1

“Raising an event” usually just means “calling a delegate” – but potentially a multicast delegate with many invocations in its list. Each of these is pretty cheap… not much more than a direct method call usually, although there are situations which are more expensive. (IIRC, call a delegate which has been created via an interface method is more expensive.)

I strongly recommend that you write the most natural code to start with, and then test it to see if it performs well enough. I can’t immediately think of a quicker way to effectively call a bunch of subscriber methods. I suspect it’s generally as cheap as iterating over a list of interface implementations and calling an interface method on each, and it may well be significantly cheaper in some situations.