前台HTML文件代码（Register.aspx）：
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
??? <title></title>
??? <script src="Scripts/jquery-1.7.2.js" type="text/javascript"></script>
??? <script type="text/javascript">
??????? $(function () {
??????????? function CheckCode() {
??????????????? AJAX_Work.WebService1.CheckCode($('#txtName').val(),onSuccess,onFailed);
??????????? }
??????????? function onSuccess(result) {
??????????????? if (result == true) {
??????????????????? $('#yanzheng').append('<a style="color:green;"><samp>用户名可以使用！</samp></a>');
?????????????????????????????????? }
??????????????? else {
??????????????????? $('#yanzheng').append('<a style="color:red;"><samp>用户名不可以使用！</samp></a>');
????????????????????
??????????????? }
??????????? }
??????????? function onFailed() {
??????????????? alert('调用失败');
??????????? }
??????????? $('#txtName').blur(function () {
//调用上面的方法。
??????????????? CheckCode();
??????????? })
??????? })
??? </script>
//页面比较简单，表格也是鼠标拖成的这些是自动生成的一些个样式
??? <style type="text/css">
??????? .style1
??????? {
??????????? width: 100%;
??????? }
??????? .style2
??????? {
??????????? width: 157px;
??????? }
??????? .style3
??????? {
??????????? width: 67px;
??????? }
??? </style>
</head>
<body>
??? <form id="form1" runat="server">
??? <asp:ScriptManager ID="ScriptManager1" runat="server">
??????? <Services>
//引用Web服务文件
??????????? <asp:ServiceReference Path="~/WebService1.asmx" />
??????? </Services>
??? </asp:ScriptManager>
??? <div>
??????? <table class="style1">
??????????? <tr>
??????????????? <td align="left" class="style3">
??????????????????? 用户名：
??????????????? </td>
??????????????? <td class="style2">
??????????????????? <asp:TextBox ID="txtName" runat="server"></asp:TextBox>
??????????????? </td>
??????????????? <td id="yanzheng">
??????????????????? <asp:Label ID="Label1" runat="server" ForeColor="Red" Text="*"></asp:Label>
??????????????? </td>
??????????? </tr>
??????????? <tr>
??????????????? <td align="left" class="style3">
??????????????????? 密 码：
??????????????? </td>
??????????????? <td class="style2">
??????????????????? <asp:TextBox ID="txtPass" runat="server"></asp:TextBox>
??????????????? </td>
??????????????? <td>
???????????????????
??????????????? </td>
??????????? </tr>
??????????? <tr>
??????????????? <td align="left" colspan="2">
??????????????????? <asp:Button ID="Button2" runat="server" Text="注?? 册" XonClick="Button2_Click" />
??????????????? </td>
??????????????? <td>
???????????????????
??????????????? </td>
??????????? </tr>
??????? </table>
??? </div>
??? <div id="newdiv">
??? </div>
??? </form>
</body>
</html>
下面是Web服务文件的内容
Web服务文件（WebService1.asmx）：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Configuration;
using System.Data.SqlClient;
namespace AJAX_Work
{
??? /// <summary>
??? /// WebService1 的摘要说明
??? /// </summary>
??? [WebService(Namespace = "http://tempuri.org/")]
??? [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
??? [System.ComponentModel.ToolboxItem(false)]
??? // 若要允许使用 ASP.NET AJAX 从脚本中调用此 Web 服务，请取消对下行的注释。
?? [System.Web.Script.Services.ScriptService]
??? public class WebService1 : System.Web.Services.WebService
??? {
??????? string str = ConfigurationManager.ConnectionStrings["sqlcon"].ConnectionString;
??????? [WebMethod]
??????? public string HelloWorld()
??????? {
??????????? return "Hello World";
??????? }
//这里是查询数据库中是否有相同的记录，如果有则返回布尔值False表示当前的值是不可用的
??????? [WebMethod]
??????? public bool CheckCode(string name)
??????? {
??????????? SqlConnection sqlcon = new SqlConnection(str);
??????????? SqlCommand sqlcom = sqlcon.CreateCommand();
??????????? sqlcon.Open();
??????????? sqlcom.CommandText = "select count(*) from T_Users where Uname=@name"; ??????????? sqlcom.Parameters.AddWithValue("@name",name); ???????????? int? obj=Convert.ToInt32( sqlcom.ExecuteScalar());? ??????????? sqlcon.Dispose(); ????????????? sqlcom.Dispose(); ????????????? if (obj != 0) ????????????? { ????????????????? return false; ????????????? } ????????????? else ????????????? { ????????????????? return true; ????????????? } ??????? } ??? } }
页面功能较为简单，具有可扩展性！
