虚函数简单示例

虚函数简单地说，那些被virtual关键字修饰的成员函数。虚函数的作用，用专业术语来解释就是实现多态性（Polymorphism），多态性就是实现共同的方法，但因个体差异而采用不同的策略。
简单的示例


public class ShapeWithArea




...{


protected double x,y,area;


protected string name;




public ShapeWithArea(double x,double y)




...{


this.x=x;


this.y=y;


}




public virtual double Area()




...{


area= x*y;


return area;


}


public override string ToString()




...{


return name+"的面积是:"+Area().ToString();


}




}




public class Circle:ShapeWithArea




...{


public Circle(int r):base(r,0)




...{


base.name="圆";


}




public override double Area()




...{


return Math.PI*x*x;


}




}


public class Sphere:ShapeWithArea




...{


public Sphere(int r):base(r,0)




...{


base.name="球";


}


public override double Area()




...{


return 4*Math.PI*x*x;


}




}




public class Cylinder:ShapeWithArea




...{


public Cylinder(int r,int h):base(r,h)




...{


base.name="圆柱";


}


public override double Area()




...{


return 2*Math.PI*x*x+2*Math.PI*x*y;


}




}


//如何调用


txtinfo.Text=string.Empty;


ShapeWithArea[] test=new ShapeWithArea[3];




test[0]=new Circle(Int32.Parse(txtcircle.Text));


test[1]=new Sphere(Int32.Parse(txtsphere.Text));


test[2]=new Cylinder(Int32.Parse(txtcylinderr.Text),Int32.Parse(txtcylinderh.Text));




string info=string.Empty;


foreach(ShapeWithArea swa in test)




...{


info+=swa.ToString();


}


txtinfo.Text=info;

http://dl2.csdn.net/down4/20070715/15115143803.rar

示例工程文件