| 2.清单9-2. 带有重载方法的派生类：Line.cs, Circle.cs, and Square.cs |
using System;
public class Line : DrawingObject
{
public override void Draw()
{
Console.WriteLine("I'm a Line.");
}
}
public class Circle : DrawingObject
{
public override void Draw()
{
Console.WriteLine("I'm a Circle.");
}
}
public class Square : DrawingObject
{
public override void Draw()
{
Console.WriteLine("I'm a Square.");
}
} |
清单9-2定义了三个类。这三个类都派生自DrawingObject类。每个类都有一个同名Draw()方法，这些Draw()方法中的每一个都有一个重载修饰符。重载修饰符可让该方法在运行时重载其基类的虚方法，实现这个功能的条件是：通过基类类型的指针变量来引用该类。
| 3.清单9-3. 实现多态性的程序：DrawDemo.cs |
using System;
public class DrawDemo
{
public static int Main(string[] args)
{
DrawingObject[] dObj = new DrawingObject[4];
dObj[0] = new Line();
dObj[1] = new Circle();
dObj[2] = new Square();
dObj[3] = new DrawingObject();
foreach (DrawingObject drawObj in dObj)
{
drawObj.Draw();
}
return 0;
}
} |
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