在当前页面显示ajax出错信息

aspx

     < form id = " form1 "  runat = " server " >
         < asp:ScriptManager ID = " ScriptManager1 "  runat = " server "  AllowCustomErrorsRedirect = " false "  OnAsyncPostBackError = " ScriptManager1_AsyncPostBackError " >
         </ asp:ScriptManager >

         < asp:UpdatePanel ID = " UpdatePanel1 "  runat = " server " >
             < ContentTemplate >
                 < asp:Button ID = " Button1 "  runat = " server "  Text = " Button "  OnClick = " Button1_Click "   />
             </ ContentTemplate >
         </ asp:UpdatePanel >
        
         < div id = " error " ></ div >
         < script type = " text/javascript "  language = " javascript " >
            Sys.WebForms.PageRequestManager.getInstance().add_endRequest(function(sender, e)
            {
                e.set_errorHandled( true );
                $ get ( " error " ).innerHTML  =   " Sorry, an error has occurred:  "   +  e.get_error().message;
                setTimeout(function(){ $ get ( " error " ).innerHTML  =   "" ; },  3000 );
            });
         </ script >
     </ form >

cs

     protected   void  Page_Load( object  sender, EventArgs e)
    {

    }
    
     protected   void  Button1_Click( object  sender, EventArgs e)
    {
         throw   new  Exception( " Custom Error! " );
    }
     protected   void  ScriptManager1_AsyncPostBackError( object  sender, AsyncPostBackErrorEventArgs e)
    {
        ScriptManager.GetCurrent( this ).AsyncPostBackErrorMessage  =  e.Exception.Message;
    }

点击Button1按钮后，会在 < div id = " error " ></ div >中显示Sorry, an error has occurred: Custom Error!，其中Custom Error就是在Button1_Click中自定义的错误信息,然后隔了三秒钟后错误信息自动消失是setTimeout(function(){ $ get ( " error " ).innerHTML  =   "" ; },  3000 );的作用。