Microsoft Asp.Net Ajax框架入门(10) ScriptManager, UpdatePanel, Timer

VS 2008

本文介绍Microsoft Asp.Net Ajax框架的服务端重要控件

1. ScriptManager
    ScriptManager控件被寓为Asp.Net Ajax的大脑，所有的Asp.Net Ajax Enabled Pages都必须包含有且仅有一个ScriptManager控件。

< asp:ScriptManager ID = " scriptMgr "  runat = " server " >
</ asp:ScriptManager >

    包含了该控件，页面便会自动引用必需的Core Library脚本文件，并生成一些页面js。

    如要现在新建了一个User.js的脚本文件，并需要在页面中注册，则改为：

< asp:ScriptManager ID = " scriptMgr "  runat = " server " >
             < Scripts >
                 < asp:ScriptReference Path = " ~/User.js "   />
             </ Scripts >
         </ asp:ScriptManager >

    
    还可注册客户端js可调用的Web Services：

< asp:ScriptManager ID = " scriptMgr "  runat = " server " >
             < Scripts >
                 < asp:ScriptReference Path = " ~/User.js "   />
             </ Scripts >
             < Services >
                 < asp:ServiceReference Path = " ~/CountrySvc.asmx "   />
             </ Services >
         </ asp:ScriptManager >

    这样，ScriptManager会为Web Service生成一个客户端脚本的web service访问代理，供客户端调用。
2. ScriptMangerProxy
    一个页面只能有一个ScriptManager控件，但，如果页面使用MasterPage, ContentPage, 通常ScriptManager会置于MasterPage，在那里注册通用的js或web service，那么，在Content Page中可能也需要注册只需要当前页面调用的js或Web Service，那么就需要用到ScriptManagerProxy控件。
    ScriptManagerProxy继承自ScriptManager。

< asp:ScriptManagerProxy ID = " sriptMgrPxy "  runat = " server " >
             < Scripts >
                 < asp:ScriptReference Path = " Company.js "   />
             </ Scripts >
             < Services >
                 < asp:ServiceReference Path = " CompanySvc.asmx "   />
             </ Services >
         </ asp:ScriptManagerProxy >

3. UpdatePanel
    UpdatePanel定义了部分页面更新的区域，html写在ContentTemplate里面
    例：
    

< asp:UpdatePanel ID = " uPanel1 "  runat = " server " >
             < ContentTemplate >
                 < asp:TextBox ID = " txtName "  runat = " server "   />
                 < asp:Button ID = " btnShowName "  runat = " server "  Text = " show name "  OnClick = " btnShowName_Click "   />
             </ ContentTemplate >
         </ asp:UpdatePanel >

protected   void  btnShowName_Click( object  sender, EventArgs e)  {
        txtName.Text = "guozhijian";
    }

    点击btnShowName控件，txtName文本框的值改变了，页面没有回刷
    
    一个页面可以包含多个UpdatePanel：

< asp:UpdatePanel ID = " uPanel1 "  runat = " server " >
             < ContentTemplate >
                 < asp:TextBox ID = " txtName "  runat = " server "   />
                 < asp:Button ID = " btnShowName "  runat = " server "  Text = " show name "  OnClick = " btnShowName_Click "   />
             </ ContentTemplate >
         </ asp:UpdatePanel >
         < asp:UpdatePanel ID = " uPanel2 "  runat = " server " >
             < ContentTemplate >
                 < asp:TextBox ID = " txtAge "  runat = " server "   />
                 < asp:Button ID = " btnShowAge "  runat = " server "  Text = " show age "  OnClick = " btnShowAge_Click "   />
             </ ContentTemplate >
         </ asp:UpdatePanel >

protected   void  btnShowName_Click( object  sender, EventArgs e)  {
        txtName.Text = "guozhijian";
    }
     protected   void  btnShowAge_Click( object  sender, EventArgs e)  {
        txtAge.Text = "26";
    }

    
    触发UpdatePanel更新的控件可以至于UpdatePanel外部，这是需要设置UpdatePanle的 UpdateMode="Conditional"，并设置UpdatePanel的<Triggers>：

< asp:UpdatePanel ID = " uPanel1 "  runat = " server "  UpdateMode = " Conditional " >
             < ContentTemplate >
                 < asp:TextBox ID = " txtName "  runat = " server "   />
             </ ContentTemplate >
             < Triggers >
                 < asp:AsyncPostBackTrigger ControlID = " btnShowName "   />
             </ Triggers >
         </ asp:UpdatePanel >
        
         < asp:Button ID = " btnShowName "  runat = " server "  Text = " show name "  OnClick = " btnShowName_Click "   />

    如果一个页面包含多个UpdatePanel，默认情况下如果任何一个UpdatePanel被触发更新，那么都会触发所有UpdatePanel的更新，为避免这一情况发生，建议总是设置UpdatePanel的UpdateMode="Conditional“，指定各自的AsyncPostBackTrigger。

4. Timer
    Timer控件用于创建一个定时执行的任务，例：在一个TextBox控件中显示当前时间，每秒刷一次

< asp:UpdatePanel ID = " uPanel1 "  runat = " server "  UpdateMode = " Conditional " >
             < ContentTemplate >
                 < asp:TextBox ID = " txtTime "  runat = " server "   />
             </ ContentTemplate >
             < Triggers >
                 < asp:AsyncPostBackTrigger ControlID = " timer1 "   />
             </ Triggers >
         </ asp:UpdatePanel >
         < asp:Timer ID = " timer1 "  OnTick = " timer1_Tick "  runat = " server "  Interval = " 1000 "   />

protected   void  timer1_Tick( object  sender, EventArgs e)  {
        txtTime.Text = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss");
    }

5. Exception Handler
    如何异步回刷请求提交后，出现异常，那么在客户端会有一个alert提示框提示异常信息

protected   void  btnShowName_Click( object  sender, EventArgs e)  {
        throw new Exception("没有取到名字");
    }

    如果，需要对页面的异步回刷请求做统一异常处理，那么可以订阅ScirptManager的AsyncPostBackError

protected   void  Page_Load( object  sender, EventArgs e)
     {
        ScriptManager mgr = ScriptManager.GetCurrent(this.Page);
        mgr.AsyncPostBackError += new EventHandler<AsyncPostBackErrorEventArgs>(mgr_AsyncPostBackError);
    }

     void  mgr_AsyncPostBackError( object  sender, AsyncPostBackErrorEventArgs e)  {
        //
        ScriptManager.GetCurrent(this.Page).AsyncPostBackErrorMessage = "we are sorry";
    }

    当ScriptManager的AsyncPostBackError事件触发时，设置 AsyncPostBackErrorMessage