Pro C# 2010 and the .NET 4 Platform, Fifth Edition

9.1. Understanding Interface Types

To begin this chapter, allow me to provide a formal definition of the interface type. An interface is nothing more than a named set of abstract members. Recall from Chapter 6 that abstract methods are pure protocol in that they do not provide a default implementation. The specific members defined by an interface depend on the exact behavior it is modeling. Yes, it's true. An interface expresses a behavior that a given class or structure may choose to support. Furthermore, as you will see in this chapter, a class (or structure) can support as many interfaces as necessary, thereby supporting (in essence) multiple behaviors.

As you might guess, the .NET base class libraries ship with hundreds of predefined interface ...