<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="AjaxCustomValid.aspx.cs" Inherits="WebApplication2.AjaxCustomValid" %><! 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 ></ title >< script  src ="JS/jquery.min.js"  type ="text/javascript" ></ script ><script type= "text/javascript" >function Valid(sender, args) {$.ajax({type: 'post' ,url: 'CustomValid.aspx' ,data: 'name=' + $( '#txtName' ).val(),success: function (result) {$( '#hidResult' ).val(result);},error: function () { $( '#hidResult' ).val( 'Fail' ); }})if ($( '#hidResult' ).val() == 'Pass' )args.IsValid = true ;elseargs.IsValid = false ;};        </ script ></ head >< body >< form  id ="form1"  runat ="server" >< div >使用者名称：< asp:TextBox  ID ="txtName"  runat ="server" ></ asp:TextBox >< br  />< asp:HiddenField  ID ="hidResult"  runat ="server"  />< asp:RequiredFieldValidator  ID ="rfvName"  runat ="server"  ErrorMessage ="请输入使用者名称"  Display ="None"ControlToValidate ="txtName" ></ asp:RequiredFieldValidator >< asp:CustomValidator  ID ="cvName"  Display ="None"  runat ="server" ClientValidationFunction ="Valid"  ErrorMessage ="该使用者名称已经存在!!!"  ControlToValidate ="txtName" ></ asp:CustomValidator >< asp:Button  ID ="Button1"  runat ="server"  Text ="Cehck!"  onclick ="Button1_Click"   />< asp:ValidationSummary  ID ="vs"  runat ="server"  ShowMessageBox ="true"  ShowSummary ="false"  /></ div ></ form ></ body ></ html >

   1:   using System;

   2:   using System.Collections.Generic;

   3:   using System.Linq;

   4:   using System.Web;

   5:   using System.Web.UI;

   6:   using System.Web.UI.WebControls;

   7:   

   8:   namespace WebApplication2

   9:   {

  10:       public  partial  class AjaxCustomValid : System.Web.UI.Page

  11:       {

  12:           protected  void Page_Load( object sender, EventArgs e)

  13:           {

  14:               Response.Write( string .Format( "系统时间：{0}<br/>" , DateTime.Now.ToString()));

  15:           }

  16:   

  17:           protected  void Button1_Click( object sender, EventArgs e)

  18:           {

  19:               if (Page.IsValid)

  20:                   Response.Write( string .Format( "使用者名称【{0}】可使用" , txtName.Text));

  21:           }

  22:       }

  23:   }

   1:   using System;

   2:   using System.Collections.Generic;

   3:   using System.Linq;

   4:   using System.Web;

   5:   using System.Web.UI;

   6:   using System.Web.UI.WebControls;

   7:   

   8:   namespace WebApplication2

   9:   {

  10:       public  partial  class CustomValid : System.Web.UI.Page

  11:       {

  12:           protected  void Page_Load( object sender, EventArgs e)

  13:           {

  14:               string name = Request.Form[ "name" ];

  15:               //这边各位可以依照自己的商业逻辑来撰写，例如资料库存取或是其他运算

  16:               if ( string .IsNullOrEmpty(name))

  17:                   Response.Write( "Fail" );

  18:               else

  19:               {

  20:                   if (name.ToUpper() == "TERRY" )

  21:                       Response.Write( "Fail" );

  22:                   else

  23:                       Response.Write( "Pass" );

  24:               }

  25:           }

  26:       }

  27:   }

注：ajax要设置成同步 async: false。这是因为ajax异步执行完设置args.IsValid时ms注册的检查这个属性是否为true的代码已经执行过了，所以ajax再设置args.IsValid就没什么作用了，不会再次触发ms注册检查args.IsValid事件。