using System;

public class Program {

    public static void Main() {

        var a = new Ball();

        ((CanRoll)a).Roll();

    }

}

​

public interface CanBounce {

  void Bounce() => Console.WriteLine("Bounce!"); 

}

​

public interface CanRoll {

   void Roll() => Console.WriteLine("Roll"); 

}

​

public class Ball : CanBounce, CanRoll {};

public class Cylinder: CanRoll {};

public class Cube : CanBounce {};