virtual members « virtual « Language Basics

The following code shows how to use the virtual method to provide the different implementation of the Area.


using System;

class Shape{
  public virtual double Area{
     get{
        return 0;
     }
  }
}


class Rectangle:Shape{
   public int width;
   public int height;
   
   public override double Area{
      get{
         return width * height;
      }
   }
}

class Circle:Shape{
   public int radius;
   
   public override double Area{
      get{
         return 3.14 * radius * radius;
      }
   }
}


class Program
{
    static void Main(string[] args)
    {
        Rectangle r = new Rectangle();
        r.width = 4;
        r.height = 5;
        Circle c = new Circle();
        c.radius = 6;
        Console.WriteLine(r.Area);
        Console.WriteLine(c.Area);

    }
}


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C# requires that the virtual and override must have the same signature, accessor and return type.