c# - Events aren't fields - I don't get it

Question

In C# in depth (an excellent book thus far), Skeet explains events aren't fields. I read this section many times and I don't understand why the distinction makes any difference.

I am one of those developers that confuse events and delegate instances. In my mind, they are the same. Aren't both just a form of indirection? We can multicast both. An event is setup as a field as shorthand...sure. But, we are adding or removing handlers. Stacking them up to be called when the event fires. Don't we do the same thing with delegates, stack them up and call invoke?

Answer 1

The other answers are basically correct, but here's another way to look at it:

I am one of those developers that confuse events and delegate instances. In my mind, they are the same.

An old saying about not seeing the forest for the trees comes to mind. The distinction that I make is that events are at a higher "semantic level" than a field of delegate instance. An event tells the consumer of the type "hi there, I am a type that likes to tell you when something happens". The type sources an event; that's part of its public contract.

How, as an implementation detail, that class chooses to keep track of who is interested in listening to that event, and what and when to tell the subscribers that the event is happening, is the business of the class. It happens to typically do so with a multicast delegate, but that's an implementation detail. It is such a common implementation detail that it is reasonable to confuse the two, but we really do have two different things: a public surface, and a private implementation detail.

Similarly, properties describe the semantics of an object: a customer has a name, so a Customer class has a Name property. You might say that "their name" is a property of a customer, but you would never say that "their name" is a field of a customer; that's an implementation detail of a particular class, not a fact about the business semantics. That a property is typically implemented as a field is a private detail of the class mechanics.