Events in C#

An event is just an accessor (+=, -=) to a field holding a MulticastDelegate. The difference between a publicly accessible delegate field and an event are the following:

you cannot

Declaration

public event <delegate_type> <event_name>;

The compiler creates a private field with the same name.

private <delegate_type> <event_name>;

Quick Facts

Fireing an Event that has not been registered (==null) raises a NullReferenceException. (annoying)
Registering for the same event twice with the same delegate means that the delegate will be called twice.
A delegate that has been registered for the same event multiple times must also be unregistered multiple times.
Unregistering an event that has never been registered (using -= on a null event) has no effect.
There is no built-in mechanism for preventing event recursions. (see Preventing Recursive Events)