乐在其中设计模式(C#) - 观察者模式(Observer Pattern)

using System; 
using System.Collections.Generic; 
using System.Text; 
 
namespace Pattern.Observer 
{ 
         /// <summary> 
         /// Message实体类 
         /// </summary> 
         public  class MessageModel 
        { 
                 /// <summary> 
                 /// 构造函数 
                 /// </summary> 
                 /// <param name="msg">Message内容</param> 
                 /// <param name="pt">Message发布时间</param> 
                 public MessageModel( string msg, DateTime pt) 
                { 
                         this._message = msg; 
                         this._publishTime = pt; 
                } 
 
                 private  string _message; 
                 /// <summary> 
                 /// Message内容 
                 /// </summary> 
                 public  string Message 
                { 
                        get {  return _message; } 
                        set { _message = value; } 
                } 
 
                 private DateTime _publishTime; 
                 /// <summary> 
                 /// Message发布时间 
                 /// </summary> 
                 public DateTime PublishTime 
                { 
                        get {  return _publishTime; } 
                        set { _publishTime = value; } 
                } 
        } 
}

using System; 
using System.Collections.Generic; 
using System.Text; 
 
namespace Pattern.Observer 
{ 
         /// <summary> 
         /// 操作Message的接口（Observer） 
         /// </summary> 
         public  interface IMessage 
        { 
                 /// <summary> 
                 /// 插入Message 
                 /// </summary> 
                 /// <param name="mm">Message实体对象</param> 
                 /// <returns></returns> 
                 string Insert(MessageModel mm); 
        } 
}

using System; 
using System.Collections.Generic; 
using System.Text; 
 
namespace Pattern.Observer 
{ 
         /// <summary> 
         /// Sql方式操作Message（ConcreteObserver） 
         /// </summary> 
         public  class SqlMessage : IMessage 
        { 
                 /// <summary> 
                 /// 插入Message 
                 /// </summary> 
                 /// <param name="mm">Message实体对象</param> 
                 /// <returns></returns> 
                 public  string Insert(MessageModel mm) 
                { 
                         return  "sql方式：" + mm.Message +  " " + mm.PublishTime.ToString(); 
                }    
        } 
}

using System; 
using System.Collections.Generic; 
using System.Text; 
 
namespace Pattern.Observer 
{ 
         /// <summary> 
         /// Xml方式操作Message（ConcreteObserver） 
         /// </summary> 
         public  class XmlMessage : IMessage 
        { 
                 /// <summary> 
                 /// 插入Message 
                 /// </summary> 
                 /// <param name="mm">Message实体对象</param> 
                 /// <returns></returns> 
                 public  string Insert(MessageModel mm) 
                { 
                         return  "xml方式：" + mm.Message +  " " + mm.PublishTime.ToString(); 
                }    
        } 
}

using System; 
using System.Collections.Generic; 
using System.Text; 
 
namespace Pattern.Observer 
{ 
         /// <summary> 
         /// 抽象Message主题（Subject） 
         /// </summary> 
         public  abstract  class AbstractMessageSubject 
        { 
                 private MessageModel _messageModel; 
                 private List<IMessage> list =  new List<IMessage>(); 
 
                 /// <summary> 
                 /// 构造函数 
                 /// </summary> 
                 /// <param name="mm">Message实体对象</param> 
                 public AbstractMessageSubject(MessageModel mm) 
                { 
                         this._messageModel = mm; 
                } 
 
                 /// <summary> 
                 /// 添加一个实现IMessage接口的对象 
                 /// </summary> 
                 /// <param name="m">实现IMessage接口的对象</param> 
                 public  void Attach(IMessage m) 
                { 
                        list.Add(m); 
                } 
 
                 /// <summary> 
                 /// 移除一个实现IMessage接口的对象 
                 /// </summary> 
                 /// <param name="m">实现IMessage接口的对象</param> 
                 public  void Detach(IMessage m) 
                { 
                        list.Remove(m); 
                } 
 
                 /// <summary> 
                 /// 通知所有观察者 
                 /// </summary> 
                 /// <returns></returns> 
                 public  string Notify() 
                { 
                         string s = ""; 
                         foreach (IMessage i  in list) 
                        { 
                                s += i.Insert(_messageModel); 
                                s +=  "<br />"; 
                        } 
 
                         return s; 
                } 
 
                 /// <summary> 
                 /// Message发布时间 
                 /// </summary> 
                 public DateTime PublishTime 
                { 
                        get {  return _messageModel.PublishTime; } 
                        set 
                        { 
                                _messageModel.PublishTime = value; 
                                Notify(); 
                        } 
                } 
        } 
}

using System; 
using System.Collections.Generic; 
using System.Text; 
 
namespace Pattern.Observer 
{ 
         /// <summary> 
         /// Message主题（ConcreteSubject） 
         /// </summary> 
         public  class MessageSubject : AbstractMessageSubject 
        { 
                 /// <summary> 
                 /// 构造函数 
                 /// </summary> 
                 /// <param name="mm">Message实体对象</param> 
                 public MessageSubject(MessageModel mm) 
                        :  base(mm) 
                { 
    
                } 
        } 
}

using System; 
using System.Data; 
using System.Configuration; 
using System.Collections; 
using System.Web; 
using System.Web.Security; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
using System.Web.UI.WebControls.WebParts; 
using System.Web.UI.HtmlControls; 
 
using Pattern.Observer; 
 
public partial  class Observer : System.Web.UI.Page 
{ 
         protected  void Page_Load( object sender, EventArgs e) 
        { 
                MessageSubject m =  new MessageSubject( new MessageModel( "插入Message", DateTime.Now)); 
 
                SqlMessage sqlMessage =  new SqlMessage(); 
                XmlMessage xmlMessage =  new XmlMessage(); 
 
                m.Attach(sqlMessage); 
                m.Attach(xmlMessage); 
 
                 // System.Threading.Thread.Sleep(1000); 
                 // 修改了PublishTime就会通知所有观察者 
                 // m.PublishTime = DateTime.Now; 
                 
                Response.Write(m.Notify()); 
        } 
}