#384 – The Difference Between Delegates and Events

Delegates are not the same thing as events in C#.

Delegates

• A delegate type defines a signature for a method (number and type of parameters and return type)
• A delegate instance is an instance of a delegate type that can refer to one or more methods
• Can add/remove handlers using the +=, -= operators
• Can invoke handlers by calling delegate instance like a method

Events

• Is a class member representing something that the class might notify calling code about
• Declared in the class like a field, whose type is a delegate type
• Wraps a private member variable that is a delegate instance
• Wraps private methods that add/remove methods to the delegate instance’s invocation list
• Client code can add/remove handlers using the +=, -= operators
• Client code can’t invoke directly

Basically, an event is a mechanism that uses a delegate to notify client code of something without exposing the delegate’s invocation list to the client.