乐在其中设计模式(C#) - 策略模式(Strategy Pattern)

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乐在其中设计模式(C#) - 策略模式(Strategy Pattern)

作者： webabcd


介绍
定义一系列的算法，把它们一个个封装起来，并且使它们可相互替换。本模式使得算法的变化可独立于使用它的客户。


示例
有一个Message实体类，对它的操作有Insert()和Get()方法，持久化数据在SqlServer数据库中或Xml文件里（两种可互换的算法）。由客户端决定使用哪种算法。

 

MessageModel

using System; 
using System.Collections.Generic; 
using System.Text; 
 
namespace Pattern.Strategy 
{ 
         /// <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; } 
                } 
        } 
}

 

IMessageStrategy

using System; 
using System.Collections.Generic; 
using System.Text; 
 
namespace Pattern.Strategy 
{ 
         /// <summary> 
         /// 策略接口 
         /// </summary> 
         public  interface IMessageStrategy 
        { 
                 /// <summary> 
                 /// 获取Message 
                 /// </summary> 
                 /// <returns></returns> 
                List<MessageModel> Get(); 
 
                 /// <summary> 
                 /// 插入Message 
                 /// </summary> 
                 /// <param name="mm">Message实体对象</param> 
                 /// <returns></returns> 
                 bool Insert(MessageModel mm); 
        } 
}

 

SqlMessage

using System; 
using System.Collections.Generic; 
using System.Text; 
 
namespace Pattern.Strategy 
{ 
         /// <summary> 
         /// Sql方式操作Message 
         /// </summary> 
         public  class SqlMessage : IMessageStrategy 
        { 
                 /// <summary> 
                 /// 获取Message 
                 /// </summary> 
                 /// <returns></returns> 
                 public List<MessageModel> Get() 
                { 
                        List<MessageModel> l =  new List<MessageModel>(); 
                        l.Add( new MessageModel( "SQL方式获取Message", DateTime.Now)); 
 
                         return l; 
                } 
 
                 /// <summary> 
                 /// 插入Message 
                 /// </summary> 
                 /// <param name="mm">Message实体对象</param> 
                 /// <returns></returns> 
                 public  bool Insert(MessageModel mm) 
                { 
                         // 代码略 
                         return  true; 
                } 
        } 
}

 

XmlMessage

using System; 
using System.Collections.Generic; 
using System.Text; 
 
namespace Pattern.Strategy 
{ 
         /// <summary> 
         /// Xml方式操作Message 
         /// </summary> 
         public  class XmlMessage : IMessageStrategy 
        { 
                 /// <summary> 
                 /// 获取Message 
                 /// </summary> 
                 /// <returns></returns> 
                 public List<MessageModel> Get() 
                { 
                        List<MessageModel> l =  new List<MessageModel>(); 
                        l.Add( new MessageModel( "XML方式获取Message", DateTime.Now)); 
 
                         return l; 
                } 
 
                 /// <summary> 
                 /// 插入Message 
                 /// </summary> 
                 /// <param name="mm">Message实体对象</param> 
                 /// <returns></returns> 
                 public  bool Insert(MessageModel mm) 
                { 
                         // 代码略 
                         return  true; 
                } 
        } 
}

 

Message

using System; 
using System.Collections.Generic; 
using System.Text; 
 
namespace Pattern.Strategy 
{ 
         /// <summary> 
         /// Context类 
         /// </summary> 
         public  class Message 
        { 
                 /// <summary> 
                 /// 声明一个IMessageStrategy类型 
                 /// </summary> 
                 private IMessageStrategy _strategy; 
 
                 /// <summary> 
                 /// 构造函数 
                 /// </summary> 
                 /// <param name="strategy">具体算法</param> 
                 public Message(IMessageStrategy strategy) 
                { 
                         this._strategy = strategy; 
                } 
 
                 /// <summary> 
                 /// 获取Message 
                 /// </summary> 
                 /// <returns></returns> 
                 public List<MessageModel> Get() 
                { 
                         return _strategy.Get(); 
                } 
 
                 /// <summary> 
                 /// 插入Message 
                 /// </summary> 
                 /// <param name="mm">Message实体对象</param> 
                 /// <returns></returns> 
                 public  bool Insert(MessageModel mm) 
                { 
                         return _strategy.Insert(mm); 
                } 
        } 
}

 

client

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.Strategy; 
 
public partial  class Strategy : System.Web.UI.Page 
{ 
         protected  void Page_Load( object sender, EventArgs e) 
        { 
                Message m =  new Message( new XmlMessage()); 
                Response.Write(m.Insert( new MessageModel( "插入", DateTime.Now))); 
                Response.Write( "<br />"); 
                Response.Write(m.Get()[0].Message +  " " + m.Get()[0].PublishTime.ToString()); 
                Response.Write( "<br />"); 
 
                m =  new Message( new SqlMessage()); 
                Response.Write(m.Insert( new MessageModel( "插入", DateTime.Now))); 
                Response.Write( "<br />"); 
                Response.Write(m.Get()[0].Message +  " " + m.Get()[0].PublishTime.ToString()); 
                Response.Write( "<br />"); 
        } 
}

 

 

运行结果
True
XML方式获取Message 2007-2-10 22:42:44
True
SQL方式获取Message 2007-2-10 22:42:44


参考
http://www.dofactory.com/Patterns/PatternStrategy.aspx


OK
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     本文转自webabcd 51CTO博客，原文链接：http://blog.51cto.com/webabcd/344586，如需转载请自行联系原作者