using System;

using System.Collections;

using System.Collections.Generic;

using System.Threading;

​

namespace Observer

{

    /// <summary>

    /// Observer Pattern Judith Bishop Jan 2007

    /// Updated by Kobel' Bohdan 2013

    /// 

    /// The Subject runs in a thread and changes its state

    /// independently. At each change, it notifies its Observers.

    /// </summary>

    public class Program

    {

        public static void Main()

        {

            Subject subject = new Subject();

            Observer observer = new Observer(subject,"Center","\t\t");

            Observer observer2 = new Observer(subject,"Right","\t\t\t\t");

            subject.Go();

​

            // Wait for user

        }

​

    }

​

    class Simulator : IEnumerable 

    {

        string [] moves = {"5","3","1","6","7"};

​

        public IEnumerator GetEnumerator() 

        {

            foreach (string element in moves)

                yield return element;

        }

    }

​

    interface ISubject

    {

        void AddObserver(IObserver observer);

        void RemoveObserver(IObserver observer);

        void NotifyObservers(string s);

    }

​

    class Subject : ISubject

    {

        public string SubjectState { get; set; }

        public List<IObserver> Observers { get; private set; }

​

        private Simulator simulator;

​

        private const int speed = 200;

​

        public Subject()

        {

            Observers = new List<IObserver>();

            simulator = new Simulator();

        }

​

        public void AddObserver(IObserver observer)

        {

            Observers.Add(observer);

        }

​

        public void RemoveObserver(IObserver observer)

        {

            Observers.Remove(observer);

        }

​

        public void NotifyObservers(string s)

        {

            foreach (var observer in Observers)

            {

                observer.Update(s);

            }

        }

​

        public void Go() 

        {

            new Thread(new ThreadStart(Run)).Start( );

        }

​

        void Run () 

        {

            foreach (string s in simulator) 

            {

                Console.WriteLine("Subject: " + s);

                SubjectState = s;

                NotifyObservers(s);

                Thread.Sleep(speed); // milliseconds

            }

        }

    }

​

    interface IObserver 

    {

        void Update(string state);

    }

​

    class Observer : IObserver

    {

        string name;

​

        ISubject subject;

​

        string state;

​

        string gap;

​

        public Observer(ISubject subject, string name, string gap)

        {

            this.subject = subject;

            this.name = name;

            this.gap = gap;

            subject.AddObserver(this);

        }

​

        public void Update(string subjectState)

        {

            state = subjectState;

            Console.WriteLine(gap + name + ": " + state);

        }

    }

}