Interfaces are an important feature in any object-oriented programming language. Using interfaces forces you to concentrate more on design in the early stages of application development. Because a clear distinction exists between the interface and the implementation, the concept of data hiding is much more prevalent than the traditional class-based programming paradigms in the past.
The .NET Framework is built using a wide variety of interfaces. By utilizing an interface design, the framework classes can grow without you having to design different ways of performing similar tasks. In other words, new implementations are added while the interfaces remain the same. This hour taught you how to use some of these .NET Framework interfaces. You also learned how to add interfaces to your own application and how a client can use the interfaces of your object. One thing is for certain: Using interfaces is possibly one of the best design decisions you can make when creating a new application.