Use virtual methods and polymorphism. : Virtual : Class C# Examples

    
using  System;  
  
class  Shape  {    
    double  pri_width;    //  private  
    double  pri_height;  //  private  
    string  pri_name;      //  private  
    
    public  Shape()  {    
        width  =  height  =  0.0;    
        name  =  "null";    
    }    
    
    public  Shape(double  w,  double  h,  string  n)  {    
        width  =  w;    
        height  =  h;    
        name  =  n;    
    }    
    
    public  Shape(double  x,  string  n)  {    
        width  =  height  =  x;    
        name  =  n;    
    }    
    
    public  Shape(Shape  ob)  {    
        width  =  ob.width;    
        height  =  ob.height;    
        name  =  ob.name;    
    }    
    
    //  Properties  for  width,  height,  and  name  
    public  double  width  {  
        get  {  return  pri_width;  }  
        set  {  pri_width  =  value;  }  
    }  
  
    public  double  height  {  
        get  {  return  pri_height;  }  
        set  {  pri_height  =  value;  }  
    }  
  
    public  string  name  {  
        get  {  return  pri_name;  }  
        set  {  pri_name  =  value;  }  
    }  
    
    public  void  showDim()  {    
        Console.WriteLine("Width  and  height  are  "  +    
                                              width  +  "  and  "  +  height);    
    }    
    
    public  virtual  double  area()  {      
        Console.WriteLine("area()  must  be  overridden");    
        return  0.0;    
    }      
}    
    
class  Triangle  :  Shape  {    
    string  style;  //  private  
        
    public  Triangle()  {    
        style  =  "null";    
    }    
    
    public  Triangle(string  s,  double  w,  double  h)  :  
        base(w,  h,  "triangle")  {    
            style  =  s;      
    }    
    
    public  Triangle(double  x)  :  base(x,  "triangle")  {    
        style  =  "isosceles";      
    }    
    
    public  Triangle(Triangle  ob)  :  base(ob)  {    
        style  =  ob.style;    
    }    
    
    //  Override  area()  for  Triangle.  
    public  override  double  area()  {    
        return  width  *  height  /  2;    
    }    
    
    //  Display  a  triangle's  style.  
    public  void  showStyle()  {    
        Console.WriteLine("Triangle  is  "  +  style);    
    }    
}    
    
class  Rectangle  :  Shape  {      
    public  Rectangle(double  w,  double  h)  :  base(w,  h,  "rectangle"){  }    
    
    public  Rectangle(double  x)  :  base(x,  "rectangle")  {  }    
    
    //  Construct  an  object  from  an  object.    
    public  Rectangle(Rectangle  ob)  :  base(ob)  {  }    
    
    //  Return  true  if  the  rectangle  is  square.  
    public  bool  isSquare()  {      
        if(width  ==  height)  return  true;      
        return  false;      
    }      

    //  Override  area()  for  Rectangle.  
    public  override  double  area()  {      
        return  width  *  height;      
    }      
}    
    
class  DynShapes  {    
    public  static  void  Main()  {    
        Shape[]  shapes  =  new  Shape[5];    
    
        shapes[0]  =  new  Triangle("right",  8.0,  12.0);    
        shapes[1]  =  new  Rectangle(10);    
        shapes[2]  =  new  Rectangle(10,  4);    
        shapes[3]  =  new  Triangle(7.0);    
        shapes[4]  =  new  Shape(10,  20,  "generic");  
    
        for(int  i=0;  i  <  shapes.Length;  i++)  {    
            Console.WriteLine("object  is  "  +  shapes[i].name);    
            Console.WriteLine("Area  is  "  +  shapes[i].area());    
    
            Console.WriteLine();        
        }    
    }    
}