Classes and Inheritance - Illustrated C# 2005 - page 140

Class Inheritance
Inheritance allows you to define a new class that incorporates and extends an already
declared class.

• You can use an existing class, called the base class , as the basis for a new class, called the

derived class . The members of the derived class consist of the following:
- The members in its own declaration

- The members of the base class

￿ To declare a derived class, you add a class-base specification after the class name. The

class-base specification consists of a colon, followed by the name of the class to be used
as the base class. The derived class is said to directly inherit from the base class listed.

￿ A derived class is said to extend its base class, because it includes the members of the

base class plus any additional functionality provided in its own declaration.

￿ A derived class cannot delete any of the members it has inherited.

For example, the following shows the declaration of a class called OtherClass , which is
derived from a class called SomeClass .

Class-base specification
↓
class OtherClass : SomeClass
{ ↑ ↑
... Colon Base class
}

Figure 7-1 shows an instance of each of the classes. Class SomeClass , on the left, has one
field and one method. Class OtherClass , on the right, is derived from SomeClass and contains
an additional field and an additional method.

Figure 7-1. Base class and derived class