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from:设计模式 - Strategy Pattern(策略模式)??
[源码下载]
设计模式 - Strategy Pattern(策略模式)
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 OK [源码下载]
（编辑：李大同）
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