Asp.net 回调机制

前台aspx:

< %@ Page Language = " C# "  AutoEventWireup = " true "   CodeFile = " Default.aspx.cs "  Inherits = " _Default "  % >

< !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 > CallBack Page </ title >
     < script type = " text/javascript " >
         function  GetNumber() {
            UseCallback();
        }

         function  GetRandNumberFromSer(TextBox1, context) {
            document.forms[ 0 ].TextBox1.value  =  TextBox1;
        }
     </ script >
</ head >
< body >
     < form id = " form1 "  runat = " server " >
     < div >
         < input id = " Button1 "  type = " button "  value = " Get Rand Num "  onclick = " GetNumber() "   />< br  />
         < asp:TextBox ID = " TextBox1 "  runat = " server " ></ asp:TextBox >
     </ div >
    
     </ form >
</ body >
</ html >

 后台CS页面：

using  System;
using  System.Collections.Generic;
using  System.Linq;
using  System.Web;
using  System.Web.UI;
using  System.Web.UI.WebControls;

public   partial   class  _Default : System.Web.UI.Page ,System.Web.UI.ICallbackEventHandler
{
     private   string  _callbackRestule  =   "" ;
     protected   void  Page_Load( object  sender, EventArgs e)
    {
         string  cbRefer  =  Page.ClientScript.GetCallbackEventReference( this ,  " arg " ,  " GetRandNumberFromSer " ,  " context " );
         string  cbScript  =   " function UseCallback(arg,context) "   +   " { "   +  cbRefer  +   " ; "   +   " } " ;

        Page.ClientScript.RegisterClientScriptBlock( this .GetType(),  " UseCallback " , cbScript,  true );
    }

     public   void  RaiseCallbackEvent( string  eventArg)
    {
        Random rnd  =   new  Random();
        _callbackRestule  =  rnd.Next().ToString();
    }

     public   string  GetCallbackResult()
    {
         return  _callbackRestule;
    }
}

 

生成的浏览页面源码：

<! 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 >< title >
    CallBack Page
</ title >
     < script  type ="text/javascript" >
         function  GetNumber() {
            UseCallback();
        }
         function  GetRandNumberFromSer(TextBox1, context) {
            document.forms[ 0 ].TextBox1.value  =  TextBox1;
        }
     </ script >
</ head >
< body >
     < form  name ="form1"  method ="post"  action ="Default.aspx"  id ="form1" >
< div >
< input  type ="hidden"  name ="__EVENTTARGET"  id ="__EVENTTARGET"  value =""   />
< input  type ="hidden"  name ="__EVENTARGUMENT"  id ="__EVENTARGUMENT"  value =""   />
< input  type ="hidden"  name ="__VIEWSTATE"  id ="__VIEWSTATE"  value ="/wEPDwUJMjgzMDgzOTgzZGSopwuMyHhFr03Z7y0kgY8Ughlkyg=="   />
</ div >

< script  type ="text/javascript" >
// <![CDATA[
var  theForm  =  document.forms[ ' form1 ' ];
if  ( ! theForm) {
    theForm  =  document.form1;
}
function  __doPostBack(eventTarget, eventArgument) {
     if  ( ! theForm.onsubmit  ||  (theForm.onsubmit()  !=   false )) {
        theForm.__EVENTTARGET.value  =  eventTarget;
        theForm.__EVENTARGUMENT.value  =  eventArgument;
        theForm.submit();
    }
}
// ]]>
</ script >

< script  src ="/WebSite1/WebResource.axd?d=_CLnVr0GkJ8I80CCN-XxtA2&amp;t=633809228264971767"  type ="text/javascript" ></ script >

< script  type ="text/javascript" >
// <![CDATA[
function  UseCallback(arg,context){WebForm_DoCallback( ' __Page ' ,arg,GetRandNumberFromSer,context, null , false );} // ]]>
</ script >
< div >
     < input  type ="hidden"  name ="__EVENTVALIDATION"  id ="__EVENTVALIDATION"  value ="/wEWAgKT8YSWCwLs0bLrBkZdKNW+68rz1y5Ky5Wg/oK9Jpwj"   />

</ div >
     < div >
         < input  id ="Button1"  type ="button"  value ="Get Rand Num"  onclick ="GetNumber()"   />< br  />
         < input  name ="TextBox1"  type ="text"  id ="TextBox1"   />
     </ div >

< script  type ="text/javascript" >
// <![CDATA[
WebForm_InitCallback(); // ]]>
</ script >
</ form >
</ body >
</ html >