五.Action Pattern(命令模式)

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

< html  xmlns ="http://www.w3.org/1999/xhtml"   >
< head  runat ="server" >
     < title > Untitled Page </ 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 ="ActionPattern"   />         
         < select  id ="strategy_select"  runat ="server" >
             < option  value ="A"  selected ="selected" > Begin </ option >
             < option  value ="B" > Stop </ 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.Web.UI;
using  System.Web.UI.WebControls;
using  System.Web.UI.WebControls.WebParts;
using  System.Web.UI.HtmlControls;

///   <summary>
///  命名模式
///  好處:1.把執行動作和命令分開,可以隨意新增動作皆點,然後統一一個命令類去調用.
///       2.很容易的設計一個動作對列,一個一個執行.還很方便的Undo前一個動作產生的效果.
///  缺點:當一個系統動作較多的時候,比如超過500以上的動作的時候,這種模式就會產生500個動作類,這樣實現起來有點不實際.
///  
///   </summary>
public  partial  class  Pattern_Action_Pattern : System.Web.UI.Page
{
     protected   void  Page_Load( object  sender, EventArgs e)
    {

    }
     protected   void  bt_submit_Click( object  sender, EventArgs e)
    {
        Doing d  =   null ;
         switch  (strategy_select.Items[strategy_select.SelectedIndex].Value.ToString())
        { 
             case   " A " :
                d  =   new  Begin();
                 break ;
             case   " B " :
                d  =   new  Stop();
                 break ;
             default :
                 break ;
        }                
        Command c  =   new  ConcreteCommand(d);
        Invoker i  =   new  Invoker();
        i.SetCommand(c);
        tb_result.Text  =  i.ExecuteCommand();
    }
}
///   <summary>
///  定義一個命令抽象類
///   </summary>
public   abstract   class  Command
{
     protected  Doing doing;
     public  Command(Doing _doing)
    {
         this .doing  =  _doing;
    }

     public   abstract   string  Execute();
}

///   <summary>
///  定義一個動作抽象類
///   </summary>
public   abstract   class  Doing
{
     public   abstract   string  DoAction();
}

///   <summary>
///  具體的動作類
///   </summary>
public   class  Begin : Doing
{
     public   override   string  DoAction()
    {
         return   " Begin Action " ;
    }
}
public   class  Stop : Doing
{
     public   override   string  DoAction()
    {
         return   " Stop Action " ;
    }
}

///   <summary>
///  具體的命令類
///   </summary>
class  ConcreteCommand : Command
{
     public  ConcreteCommand(Doing doing) :  base (doing) { }
     public   override   string  Execute()
    {
         return  doing.DoAction();
    }
}

///   <summary>
///  調用命令.由命令啟動動作執行
///   </summary>
class  Invoker
{
     public  Command command;
     public   void  SetCommand(Command _command)
    {
        command  =  _command;
    }
     public   string  ExecuteCommand()
    {
         return  command.Execute();
    }
}