Raising and handling events
Methods are often described as actions that an object can perform, either on itself or to related objects. For example, List can add an item to itself or clear itself, and File can create or delete a file in the filesystem.
Events are often described as actions that happen to an object. For example, in a user interface, Button has a Click event, a click being something that happens to a button. Another way of thinking of events is that they provide a way of exchanging messages between two objects.
Events are built on delegates, so let's start by having a look at how delegates work.
Calling methods using delegates
You have already seen the most common way to call or execute a method: use the . operator to access the method using its name. For example, Console.WriteLine tells the Console type to access its WriteLine method.
The other way to call or execute a method is to use a delegate. If you have used languages that support function...