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.youkuaiyun.com/down4/20070715/15115143803.rar

示例工程文件