一.Strategy Pattern(策略模式)

其它模式:

     一.Strategy Pattern(策略模式)
   二.Template Method Pattern(模版方法模式)
    三.Bridge Pattern(橋接模式)
   四.Visitor Pattern(訪問者模式)

<% @ Page Language="C#" AutoEventWireup="true" CodeFile="Strategy Pattern.aspx.cs" Inherits="Pattern_Strategy_Pattern"  %>

<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >

< html  xmlns ="http://www.w3.org/1999/xhtml"   >
< head  runat ="server" >
     < title > Strategy Pattern </ title >
</ head >
< body >
     < form  id ="form1"  runat ="server" >
     < div >
    
         < asp:TextBox  ID ="tb_result"  runat ="server"  TextMode ="MultiLine"  Rows ="5" ></ asp:TextBox >
         < asp:Button  ID ="bt_submit"  runat ="server"  OnClick ="bt_submit_Click"   Text ="StrategyPattern"   />     
         < select  id ="strategy_select"  runat ="server" >
             < option  value ="A"  selected ="selected" > A </ option >
             < option  value ="B" > B </ option >
             < option  value ="C" > C </ option >
         </ select >
     </ div >
     </ form >
</ body >
</ html >

using  System;
using  System.Data;
using  System.Configuration;
using  System.Collections;
using  System.Web;
using  System.Web.Security;
using  System.Text;
using  System.Web.UI;
using  System.Web.UI.WebControls;
using  System.Web.UI.WebControls.WebParts;
using  System.Web.UI.HtmlControls;

///   <summary>
///  策略模式,
///  1.使用情況:1).讓一個對象動態的選擇多種行為.2)讓一個系統動態的選擇多種算法,而且算法使用數據和內容不讓客戶端知道.
///  2.優點:1)恰當的使用了繼承,可以把行為類的很多公用代碼移到父類,這樣減少了代碼的重複性.
///  3.缺點:1)各種行為需要共同的接口,因此,在用此模式前,要清楚所有的行為.
///  4.比較:策略模式与很多其它的模式都有着广泛的联系。Strategy很容易和Bridge模式相混淆。虽然它们结构很相似，但它们却是为解决不同的问题而设计的。
///  Strategy模式注重于算法的封装，而Bridge模式注重于分离抽象和实现，为一个抽象体系提供不同的实现。Bridge模式与Strategy模式都很好的体现了"Favor composite over inheritance"的观点。
///   </summary>
public  partial  class  Pattern_Strategy_Pattern : System.Web.UI.Page
{
     protected   void  Page_Load( object  sender, EventArgs e)
    {

    }

     private   void  StrategyFactory()
    {
        Context ttt  =   null ;
         switch  (strategy_select.Items[strategy_select.SelectedIndex].Value.ToString())
        {
                
             case   " A " :
                ttt  =   new  Context( new  ConcreteStrategyA());
                tb_result.Text  =  ttt.ContextInterface(); 
                 break ;
             case   " B " :
                ttt  =   new  Context( new  ConcreteStrategyB());
                tb_result.Text  =  ttt.ContextInterface();
                 break ;
             case   " C " :
                ttt  =   new  Context( new  ConcreteStrategyC());
                tb_result.Text  =  ttt.ContextInterface();
                 break ;
             default :
                ttt  =   new  Context( new  ConcreteStrategyC());
                tb_result.Text  =  ttt.ContextInterface();
                 break ;
        }
       
    }
     protected   void  bt_submit_Click( object  sender, EventArgs e)
    {
        StrategyFactory();
    }
}

abstract   class  Strategy
{
     abstract   public   string  AlgorithmInterface();
}

class  ConcreteStrategyA : Strategy
{
     public   override   string  AlgorithmInterface()
    {
         return   " A " ;
    }
}
class  ConcreteStrategyB : Strategy
{
     public   override   string  AlgorithmInterface()
    {
         return   " B " ;
    }
}
class  ConcreteStrategyC : Strategy
{
     public   override   string  AlgorithmInterface()
    {
         return   " C " ;
    }
}
class  Context
{
    Strategy strategy;
     public  Context(Strategy strategy)
    {
         this .strategy  =  strategy;
    }
     public   string  ContextInterface()
    {
         return  strategy.AlgorithmInterface();
    }
}