EMPLOY CLASS INHERITANCE

ou can create classes with objects that more than one Yclass can refer to. Class inheritance lets you define

objects in a class once and then have other classes in your program refer to those objects.

Class inheritance speeds up the programming process by reusing code from a base class in other inheriting classes without adding extra code. You can also change objects in your base class that apply to all the inheriting classes.

Inheritance is not the best solution for all programming circumstances — interfaces can provide a better solution. See page 110 for more information on class inheritance and interfaces.

C# only gives you the ability to inherit classes from one base class. The base class is the very first class that all other classes inherit from. Like C++, you can have nested classes. Nested classes let you create classes within the class that you are programming in the MDE parent window. A nested class directly inherits from its parent class. Having nested classes makes it faster for you to create inheriting classes than if you created new classes one at a time.

You can override some base class information such as methods in your inheriting class, but for the most part inheriting classes observe the base class rules.

New Project window

.

Click the Console

Application icon in the

Templates pane.

Type a name for the file.

Click OK.

■ The Class1.cs code appears in the parent window.

Á Delete all code after the namespace Inherit code.

‡ Type the code that establishes the variables and constructors.

° Type the code that outputs the information

and the inheriting class that processes the information for output.

· Run the program by pressing the F5 key.

■ The output strings appear on the screen.

‚ Save the program as the filename.

Note: You may want to change the summary comment in the class to note to others that NewClass inherits from Class1.

class has two key parts: constructors and destructors. AA constructor is a declaration that tells the compiler

what type of class you have created, the features of your class, and how you will treat every instance of your class.

An instance is a variable of an object in the class. For example, two separate instances in the Cat class can be Mewsette and Tigger. Every member that belongs to your class has a status associated with it: static or instance.

A static member of a class belongs to the class itself, not any specific instance, and maintains a current value. This is

useful if you want to have a class of passwords with information that does not change. An instance lets you input different variables for your class. For example, if you have a Cat class, you can include various types of information such as name, weight, breed, and so on.

The instance constructor initializer is a piece of code that implements initialization of an instance of a class — in short, the piece of code that makes your class work. If you do not have a constructor in your class, C# adds one automatically — constructor initializers are that important. When you add a new class, C# adds the constructor initializer automatically.

Project in the ■ The New Project window appears.

‹ Click the Console Application icon in the Templates pane.

› Type a name for the file.

ˇ Click OK.

■ The Class1.cs code appears in the parent window.

Á Delete all code after the namespace Construct code.

‡ Type the code that establishes the integer.

°Type the Amount constructor that sets the initial value.

CONTINUED

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he constructor declaration can include a set of Tattributes that help define what it is the class is doing.

For example, if your class is creating a method, you can set attributes that determine how your class can be accessed. You can also add access modifiers to the class no matter what type of class you construct. These five access modifiers — public, protected internal, protected, internal, or private — determine your class accessibility.

The constructor initializer is only meant as the starting (and defining) point for the constructor itself. If you have a nested class, that nested class constructor initializer can access the parameters in the parent class constructor

initializer. For example, you can have a class with the constructor class One and the constructor of the second class can be class Two: One. The constructor initializer cannot, however, access any parameters in the constructor itself.

If you have an object in an inherited class, you can determine what class the object accesses — the base keyword tells the object to access class information from the base class, and the this keyword tells the object to access class information from the class in which it resides. If a constructor has no initializer, C# creates a base variable automatically.

— Type the output code for all three values in the Main method.