using System;

public class Program

{

    public static void Main()

    {

        /* 

        Strategy Design Pattern is useful you want to dynamically create behavior.

        */

        Animal dog = new Dog();

        Animal bird = new Bird();

        dog.SetFlyingAbility(new CannotFly()); //instantiate behavior

        bird.SetFlyingAbility(new CanFly());

        dog.TryToFly(); //call same method but different result

        bird.TryToFly();

        dog.SetFlyingAbility(new CanFly());

        dog.TryToFly();

    }

}

​

public class Animal

{

    IFly flyType = null;

    public void TryToFly() //common method

    {

        flyType.Fly();

    }

    public void SetFlyingAbility(IFly iFly) //instantiate behavior

    {

        flyType = iFly;

    }

}

​

public class Dog: Animal

{

    IFly iFly = null; //empty interface

    public Dog()

    {

        iFly = new CannotFly(); //instantiate class (can be dog or bird)

    }

}

​

public class Bird: Animal

{

    IFly iFly = null;

    public Bird()

    {

        iFly = new CanFly();

    }

}

​

public interface IFly

{

    void Fly();

}

​

public class CanFly: IFly

{

    public void Fly(){

        Console.WriteLine("I can fly");

    }

}

​

public class CannotFly: IFly

{

    public void Fly(){

        Console.WriteLine("I cannot fly");

    }

}