C# 0 The Complete Reference

A

,

B

, and 

C

,

C

 can be derived 

from 

B

, which can be derived from 

A

. When this type of situation occurs, each derived class 

inherits all of the traits found in all of its base classes. In this case, 

C

 inherits all aspects of 

B

and

A

.

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P a r t   I :  

T h e   C #   L a n g u a g e

To see how a multilevel hierarchy can be useful, consider the following program. 

In it, the derived class 

Triangle

 is used as a base class to create the derived class called 

ColorTriangle

.

ColorTriangle

 inherits all of the traits of 

Triangle

 and 

TwoDShape

 and 

adds a field called 

color

, which holds the color of the triangle.

// A multilevel hierarchy.

using System;

class TwoDShape {

  double pri_width;

  double pri_height;

  // Default constructor.

  public TwoDShape() {

    Width = Height = 0.0;

  }

  // Constructor for TwoDShape.

  public TwoDShape(double w, double h) {

    Width = w;

    Height = h;

  }

  // Construct object with equal width and height.

  public TwoDShape(double x) {

    Width = Height = x;

  }

  // Properties for Width and Height.

  public double Width {

     get { return pri_width; }

     set { pri_width = value < 0 ? -value : value; }

  }

  public double Height {

     get { return pri_height; }

     set { pri_height = value < 0 ? -value : value; }

  }

  public void ShowDim() {

    Console.WriteLine("Width and height are " +

                       Width + " and " + Height);

  }

}

// A derived class of TwoDShape for triangles.

class Triangle : TwoDShape {

  string Style; // private

  /* A default constructor. This invokes the default

     constructor of TwoDShape. */

  public Triangle() {

    Style = "null";

  }

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