using System;

public interface IShape

{

​

      void Draw();

}

​

​

public class Circle : IShape

    {

        public void Draw()

        {

            Console.WriteLine("Circle object's draw method\n");

        }

    }

​

    public class Rectangle : IShape

    {

        public virtual void Draw()

        {

            Console.WriteLine("Rectangle object draw method\n");

        }

    }

​

    public class Square : Rectangle

    {

        public override  void Draw()

        {

            Console.WriteLine("Square object draw method\n");

        }

    }

​

​

    public class Program

{

    public static void Main()

    {

        Console.WriteLine("Interface Test Program");

        //1

        IShape circle1 = new Circle();

        // Valid

        //2

        Rectangle rectangle2 = new Rectangle();

        // Valid

        //3

        Rectangle rectangle3 = new Square();

        // Valid

        //4

        // Circle circle4 =  new Square();

        // Invalid. We cannot assign Square to Circle. The Circle is not a base/parent class to Square 

        //5

        // IShape shape5 = new IShape(); 

        // Invalid. we cannot create instance of Interfaces

        //6     

        Console.WriteLine("---6----\n");

        Circle circle6 = new Circle();

        circle6.Draw();

        // Valid. The draw() inside the Circle class will be executed 

        //7     

        Console.WriteLine("---7----\n");

        Rectangle rectangle7 = new Rectangle();

        rectangle7.Draw();

        rectangle7 = new Square();

        rectangle7.Draw();

        //  Valid

        //8

        Console.WriteLine("---8----\n");

        IShape shape8 = new Circle();

        shape8.Draw();

        shape8 =  new Rectangle();

        shape8.Draw();

        //Valid

        //9

        Console.WriteLine("---9----\n");

        new Circle().Draw();

        //Valid

        //10

        //new IShape().Draw();

        // Invalid. We cannot create instance of Interface

    }

}