Introduction

An interface looks like a class, but has no implementation. The only thing it contains are definitions of events, indexers, methods and/or properties. The reason interfaces only provide definitions is because they are inherited by classes and structs, which must provide an implementation for each interface member defined.

Interface characteristics

• An interface defines only the properties and method signatures and not the actual implementation. In a class declaration we implement fields, properties, methods and events. In an interface we just define what properties/methods the class should have.

• Requires that classes which implement an interface must "honour" the property and method signatures. Basically are like contracts for classes. Classes which implement an interface must implement the methods and the properties of the interface.
• Many classes can implement a particular interface method, in their own way
• An interface may inherit from multiple base interfaces
• A class may implement-inherit from multiple interfaces
• A C# class may only inherit from one class