Do you know what a delegate and event are in C#? Can you clearly explain in one-two sentences what the difference between these two is?

It might sound simple as we, .net developers, use these quite frequently. Unfortunately it isn’t that straight forward, especially when you want to be precise. Just try it now aloud.

First difficulty is when you try to differentiate between the delegate type and an instance of a delegate. Next difficulty is when you try to explain events. Your explanation may mention subscribing and unsubscribing to an event. But, hey, you can do exactly the same with a delegate instance by using exactly same “+=” and “-=”. Have you thought about this? The real difference is that with an exposed event it’s about all your external code can do. Instead with an exposed delegate instance external code can do other things like changing the whole invocation list by using “=” or invoking a delegate right away.

An event is nothing more than encapsulation convenience over delegate provided by C# language.

On a conceptual level, an event is probably much more than just some convenience, but that’s beside the point in this post.

To feel the difference all you need is to write some code. Nothing helps to understand things better than writing code and reading quality resources.

Please see below my try on understanding the difference between events and delegates. I added plenty of comments in a try to be explanatory.

Click here to see the gist

Person’s sickness event triggering is responsibility of a person’s internals (stomach, in this example) and it is correct to be encapsulated in the Person’s class, otherwise external code would be able to make a person sick (I like this double-meaning).

Next step is to understand what C# compiler generates when you use the ‘event’ keyword and how else you can declare an event other than in a field-like style. I don’t describe it in this post, I’ve only read about these details, but they are quite interesting as well.

Proficiency in programming language comes with a deep understanding of the basics. I’m proving this to myself every now and then.