<<< Abstraction: Abstract Class

using System;

namespace AbstractClass {

  abstract class MotorBike {

    public abstract void brake();

  }

  class SportsBike : MotorBike {

    // provide implementation of abstract method

    public override void brake() {

      Console.WriteLine("Sports Bike Brake");

    }

  }

  class MountainBike : MotorBike {

    // provide implementation of abstract method

    public override void brake() {      

      Console.WriteLine("Mountain Bike Brake");

    }

  }

  class Program  {

    static void Main (string [] args) {

      // create an object of SportsBike class

      SportsBike s1 = new SportsBike();  

      s1.brake();

      // create an object of MountainBike class

      MountainBike m1 = new MountainBike();

      m1.brake();

      Console.ReadLine();

    }

  }

}

Sports Bike Brake

Mountain Bike Brake