34. abstaract class and method.

 using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace abstraction.cs

{

    abstract class polyabstr

    {

        public int h, w;

        public abstract int area();

    }

    class rectangle : polyabstr

    {

        public rectangle( int h, int w )

        {

            this.h = h;

            this.w = w;

        }

        public override int area() //without override error is 'abstraction.cs.rectangle' does not implement                                                         //inherited abstract member 'abstraction.cs.polyabstr.area()'

        {

            return base.h * base.w;

        }

    }

    class Program

    {

        static void Main(string[] args)

        {

            rectangle obj = new rectangle(10, 20);

            Console.WriteLine("Area of Rectangle = " + obj.area());

            Console.Read();

        }

    }

}

OUTPUT:

Area of Rectangle = 200