class1.cs

来自DoFactory的设计模式, 由于是本人根据已有代码创建,没有NETOptimized项

// Observer pattern -- Structural example  

using System;
using System.Collections;

namespace DoFactory.GangOfFour.Observer.Structural
{

    // MainApp test application 

    class MainApp
    {
        static void Main()
        {
            // Configure Observer pattern 
            ConcreteSubject s = new ConcreteSubject();

            s.Attach(new ConcreteObserver(s, "X"));
            s.Attach(new ConcreteObserver(s, "Y"));
            s.Attach(new ConcreteObserver(s, "Z"));

            // Change subject and notify observers 
            s.SubjectState = "ABC";
            s.Notify();

            // Wait for user 
            Console.Read();
        }
    }

    // "Subject" 

    abstract class Subject
    {
        private ArrayList observers = new ArrayList();

        public void Attach(Observer observer)
        {
            observers.Add(observer);
        }

        public void Detach(Observer observer)
        {
            observers.Remove(observer);
        }

        public void Notify()
        {
            foreach (Observer o in observers)
            {
                o.Update();
            }
        }
    }

    // "ConcreteSubject" 

    class ConcreteSubject : Subject
    {
        private string subjectState;

        // Property 
        public string SubjectState
        {
            get { return subjectState; }
            set { subjectState = value; }
        }
    }

    // "Observer" 

    abstract class Observer
    {
        public abstract void Update();
    }

    // "ConcreteObserver" 

    class ConcreteObserver : Observer
    {
        private string name;
        private string observerState;
        private ConcreteSubject subject;

        // Constructor 
        public ConcreteObserver(
          ConcreteSubject subject, string name)
        {
            this.subject = subject;
            this.name = name;
        }

        public override void Update()
        {
            observerState = subject.SubjectState;
            Console.WriteLine("Observer {0}'s new state is {1}",
              name, observerState);
        }

        // Property 
        public ConcreteSubject Subject
        {
            get { return subject; }
            set { subject = value; }
        }
    }
}