1: using System;

   2: using System.Collections;

   3:  

   4: namespace Autumoon.DesignPatterns.Observer

   5: {

   6:     public class Country

   7:     {

   8:         public string Name { get; set; }

   9:         public string Status { get; set; }

  10:         private ArrayList _observers = null;

  11:  

  12:         public Country()

  13:         {

  14:             this.Status = "No War.";

  15:             this._observers = new ArrayList();

  16:         }

  17:  

  18:         public void Attach(ObserverDemo observer)

  19:         {

  20:             this._observers.Add(observer);

  21:             observer.ObservedCountry = this;

  22:         }

  23:  

  24:         public void Detach(ObserverDemo observer)

  25:         {

  26:         }

  27:  

  28:         public void Notify()

  29:         {

  30:             foreach (ObserverDemo observer in this._observers)

  31:             {

  32:                 observer.Update();

  33:             }

  34:         }

  35:     }

  36:  

  37:     public class ConcreteCountry : Country

  38:     {

  39:         public string State { get; set; }

  40:     }

  41:  

  42:     abstract public class ObserverDemo

  43:     {

  44:         public Country ObservedCountry { get; set; }

  45:  

  46:         abstract public void Update();

  47:     }

  48:  

  49:     public class ConcreteObserver : ObserverDemo

  50:     {

  51:         public string Name { get; set; }

  52:  

  53:         public ConcreteObserver(string name)

  54:         {

  55:             this.Name = name;

  56:         }

  57:  

  58:         override public void Update()

  59:         {

  60:             Console.WriteLine(this.Name + ": " + this.ObservedCountry.Status);

  61:         }

  62:     }

  63: }

   1: static void Main(string[] args)

   2: {

   3:     #region Observer

   4:     ConcreteCountry country = new ConcreteCountry();

   5:     country.Name = "Uganda";

   6:  

   7:     ConcreteObserver chineseObserver = new ConcreteObserver("Chinese observer");

   8:     ConcreteObserver americanObserver = new ConcreteObserver("American observer");

   9:  

  10:     country.Attach(chineseObserver);

  11:     country.Attach(americanObserver);

  12:  

  13:     country.Status = "There's no war.";

  14:     country.Notify();

  15:  

  16:     country.Status = "There's some sound of gun in somewhere.";

  17:     #endregion

  18:  

  19:     Console.ReadLine();

  20: }