Stephens' C# Programming with Visual Studio® 2010 24-Hour Trainer

Using Interfaces

In .NET programming, an interface is like a contract. It defines the public properties, methods,

and events that a class must provide to satisfy the contract. It doesn’t indicate how the class must

provide these features, however. That’s left up to the class’s code. It only defines an interface that

the class must show to the rest of the world.

In this lesson, you learn how to implement interfaces that are predefined by .NET namespaces.

You also learn how to define your own interfaces to make your code safer and more efficient.

INTERFACE ADVANTAGES

The following sections discuss two of the most important advantages provided by interfaces:

multiple inheritance and code generalization.

Multiple Inheritance

Suppose you define a Vehicle class with properties such as NumberOfPassengers,

MilesPerGallon, and NumberOfCupHolders. From this class you can derive other classes

such as

Car, PickupTruck, and Bicycle.

Suppose you also define a

Domicile class that has properties such as SquareFeet,

NumberOfBedrooms, and NumberOfBathrooms. From this class you can derive Apartment,

Condo, and VacationHome.

Next you might like to derive the

MotorHome class from both Vehicle and Domicile so it

has the properties and methods of both parent classes. Unfortunately you can’t do that in

C#. In C# a class can inherit from only a single parent class.

Though a class can have only one parent, it can implem ...