Default.aspx代码:
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="zcajax_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>无标题页</title>
<script language=javascript>
function check_user_exists(form)
{
u_name=form.u_name.value;
if (u_name==null||u_name=='')
{
alert("请您输入用户名");
return false;
}
infoBoard=document.getElementById("checkInfo");
infoBoard.innerText='查询中...';
myurl=location.protocol+"//"+location.hostname+":6924/wwwroot/zcajax/aa.aspx?u_name="+u_name;
// alert(myurl);
retCode=openUrl(myurl);
alert(retCode);
switch(retCode)
{
case "-2":
infoBoard.innerHTML='<font color=red>抱歉</font>,查询失败';
break;
case "1":
infoBoard.innerHTML='<font color=red>恭喜</font>,'+u_name+'可以使用';
break;
case "0":
infoBoard.innerHTML='<font color=red>抱歉</font>,用户名'+u_name+'已经被使用';
}
return;
}
// alert(url);
function openUrl(url)
{
// alert(url);
var objxml=new ActiveXObject("Microsoft.XMLHttp")
objxml.open("GET",url,false);
objxml.send();
retInfo=objxml.responseText;
if (objxml.status=="200")
{
return retInfo;
}
else
{
return "-2";
}
}
</script>
</head>
<body>
<form name=form1 action="" method="post">
<input type=text name=u_name onBlur="check_user_exists(this.form);">
<input type=button name=checkuser value="注册" >
<span id="checkInfo"></span>
</form>
</body>
</html>
aa.cs
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
public partial class zcajax_aa : System.Web.UI.Page
{
public string aa;
protected void Page_Load(object sender, EventArgs e)
{
aa = Convert.ToString(Request.QueryString["u_name"]);
// aa = "aa";
if (aa.ToString() != "aa")
{
Response.Write("0");
}
else
{
Response.Write("1");
}
}
}
注意:aa的aspx里面什么也不能有除page指令
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="aa.aspx.cs" Inherits="zcajax_aa" %>

本文介绍了一个简单的ASP.NET AJAX应用程序实例,该程序用于检查用户名是否已被占用。通过客户端JavaScript和服务器端C#代码实现即时反馈,提高了用户体验。
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