using System;

using System.Collections.Generic;

public class Program

{

    // Behaviours

    interface ITalkBehaviour{

        String talk();

    }

    // For animals that bark

    class BarkBehaviour : ITalkBehaviour {

        public String talk() {

            return "Woof";

        }

    }

    // For animals that meow

    class MeowBehaviour : ITalkBehaviour {

        public String talk() {

            return "Meow";

        }

    }

    // Animal base class

    abstract class Animal {

        public abstract String talk();

    }

    class Dog : Animal {

        // Define a behaviour, this could be changed at runtime, unline inheritance. 

        // So you could provide a property to allow the injection of a MeowBehaviour, that

        // isn't possible with inheritance

        ITalkBehaviour talkBehaviour = new BarkBehaviour();

        public override String talk() {

            return talkBehaviour.talk();

        }

    }

    class Cat : Animal {

        ITalkBehaviour talkBehaviour = new MeowBehaviour();

        public override String talk() {

            return talkBehaviour.talk();

        }

    }

    public static void Main()

    {

        // Initialise some animals

        List<Animal> animals = new List<Animal> { 

            new Cat(),

            new Dog() 

        };

        foreach(Animal animal in animals) {

            Console.WriteLine(animal.talk());

        }

    }

}