When using delegates, two emergent roles commonly appear: broadcaster and subscriber. The broadcaster is a type that contains a delegate field. The broadcaster decides when to broadcast, by invoking the delegate. The subscribers are the method target recipients. A subscriber decides when to start and stop listening, by calling += and -= on the broadcaster’s delegate. A subscriber does not know about, or interfere with, other subscribers.

Events are a language feature that formalizes this pattern. An event is a construct that exposes just the subset of delegate features required for the broadcaster/subscriber model. The main purpose of events is to prevent subscribers from interfering with one another.