using System;

public class Program

{

    public static void Main()

    {

        var factory = new SimpleFactory();

        var product = factory.CreateProduct("Circle");

        product.Draw();

        product = factory.CreateProduct("Square");

        product.Draw();

    }

}

​

public abstract class Shape {

    public abstract void Draw();

}

​

public class Circle : Shape {

    public override void Draw() {

        Console.WriteLine("draw Circle");        

    }

}

​

public class Square : Shape {

    public override void Draw() {

        Console.WriteLine("draw Square");

    }

}

​

​

public class SimpleFactory {

    public Shape CreateProduct(String product) {

        //How to implement ?

        if(product == "Circle"){

            return new Circle();

        } else if(product == "Square"){

            return new Square();

        } else {

            Console.WriteLine("No Product");

            return null;

        }

    }

}