/// <summary>/// 抽象主题类/// </summary>public abstract class Subject{private IList<Observer> observers = new List<Observer>();/// <summary>/// 增加观察者/// </summary>/// <param name="observer"></param>public void Attach(Observer observer){observers.Add(observer);}/// <summary>/// 移除观察者/// </summary>/// <param name="observer"></param>public void Detach(Observer observer){observers.Remove(observer);}/// <summary>/// 向观察者（们）发出通知/// </summary>public void Notify(){foreach (Observer o in observers){o.Update();}}}/// <summary>/// 抽象观察者类，为所有具体观察者定义一个接口，在得到通知时更新自己/// </summary>public abstract class Observer{public abstract void Update();}/// <summary>/// 具体观察者或具体通知者，将有关状态存入具体观察者对象；在具体主题的内部状态改变时，给所有登记过的观察者发出通知。具体主题角色通常用一个具体子类实现。/// </summary>public class ConcreteSubject : Subject{private string subjectState;/// <summary>/// 具体观察者的状态/// </summary>public string SubjectState{get { return subjectState; }set { subjectState = value; }}}/// <summary>/// 具体观察者，实现抽象观察者角色所要求的更新接口，已是本身状态与主题状态相协调/// </summary>public class ConcreteObserver : Observer{private string observerState;private string name;private ConcreteSubject subject;/// <summary>/// 具体观察者用一个具体主题来实现/// </summary>public ConcreteSubject Subject{get { return subject; }set { subject = value; }}public ConcreteObserver(ConcreteSubject subject, string name){this.subject = subject;this.name = name;}/// <summary>/// 实现抽象观察者中的更新操作/// </summary>public override void Update(){observerState = subject.SubjectState;Console.WriteLine("The observer's state of {0} is {1}", name, observerState);}}

    class Program{static void Main(string[] args){// 具体主题角色通常用具体自来来实现ConcreteSubject subject = new ConcreteSubject();subject.Attach(new ConcreteObserver(subject, "Observer A"));subject.Attach(new ConcreteObserver(subject, "Observer B"));subject.Attach(new ConcreteObserver(subject, "Observer C"));subject.SubjectState = "Ready";subject.Notify();Console.Read();}}

    /// <summary>/// 抽象观察者/// </summary>public interface ISubject{void Notify();}/// <summary>/// 工作岗位，作为这里的观察者的抽象/// </summary>public abstract class JobStation{public abstract void Update();}/// <summary>/// 具体主题，这里是客户/// </summary>public class Customer : ISubject{private string customerState;private List<JobStation> observers = new List<JobStation>();/// <summary>/// 增加观察者/// </summary>/// <param name="observer"></param>public void Attach(JobStation observer){this.observers.Add(observer);}/// <summary>/// 移除观察者/// </summary>/// <param name="observer"></param>public void Detach(JobStation observer){this.observers.Remove(observer);}/// <summary>/// 客户状态/// </summary>public string CustomerState{get { return customerState; }set { customerState = value; }}public void Notify(){foreach (JobStation o in observers){o.Update();}}}/// <summary>/// 会计/// </summary>public class Accountant : JobStation{private string accountantState;private Customer customer;public Accountant(Customer customer){this.customer = customer;}/// <summary>/// 更新状态/// </summary>public override void Update(){if (customer.CustomerState == "已付款"){Console.WriteLine("我是会计，我来开具发票。");accountantState = "已开发票";}}}/// <summary>/// 出纳/// </summary>public class Cashier : JobStation{private string cashierState;private Customer customer;public Cashier(Customer customer){this.customer = customer;}public override void Update(){if (customer.CustomerState == "已付款"){Console.WriteLine("我是出纳员，我给登记入账。");cashierState = "已入账";}}}/// <summary>/// 配送员/// </summary>public class Dilliveryman : JobStation{private string dillivierymanState;private Customer customer;public Dilliveryman(Customer customer){this.customer = customer;}public override void Update(){if (customer.CustomerState == "已付款"){Console.WriteLine("我是配送员，我来发货。");dillivierymanState = "已发货";}}}

    class Program{static void Main(string[] args){Customer subject = new Customer();subject.Attach(new Accountant(subject));subject.Attach(new Cashier(subject));subject.Attach(new Dilliveryman(subject));subject.CustomerState = "已付款";subject.Notify();Console.Read();}}

    /// <summary>/// 抽象主题/// </summary>public interface ISubject{void Notify();}/// <summary>/// 声明委托/// </summary>public delegate void CustomerEventHandler();/// <summary>/// 具体主题/// </summary>public class Customer : ISubject{private string customerState;// 声明一个委托事件，类型为 CustomerEventHandlerpublic event CustomerEventHandler Update;public void Notify(){if (Update != null){// 使用事件来通知给订阅者Update();}}public string CustomerState{get { return customerState; }set { customerState = value; }}}/// <summary>/// 财务，已经不需要实现抽象的观察者类，并且不用引用具体的主题/// </summary>public class Accountant{private string accountantState;public Accountant(){ }/// <summary>/// 开发票/// </summary>public void GiveInvoice(){Console.WriteLine("我是会计，我来开具发票。");accountantState = "已开发票";}}/// <summary>/// 出纳，已经不需要实现抽象的观察者类，并且不用引用具体的主题/// </summary>public class Cashier{private string cashierState;public void Recoded(){Console.WriteLine("我是出纳员，我给登记入账。");cashierState = "已入账";}}/// <summary>/// 配送员，已经不需要实现抽象的观察者类，并且不用引用具体的主题/// </summary>public class Dilliveryman{private string dillivierymanState;public void Dilliver(){Console.WriteLine("我是配送员，我来发货。");dillivierymanState = "已发货";}}

    class Program{static void Main(string[] args){Customer subject = new Customer();Accountant accountant = new Accountant();Cashier cashier = new Cashier();Dilliveryman dilliveryman = new Dilliveryman();// 注册事件subject.Update += accountant.GiveInvoice;subject.Update += cashier.Recoded;subject.Update += dilliveryman.Dilliver;/** 以上写法也可以用下面代码来替换subject.Update += new CustomerEventHandler(accountant.GiveInvoice);subject.Update += new CustomerEventHandler(cashier.Recoded);subject.Update += new CustomerEventHandler(dilliveryman.Dilliver);*/subject.CustomerState = "已付款";subject.Notify();Console.Read();}}