HTML代码如下:
LoginValidate.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="LoginValidate.aspx.cs" Inherits="LoginValidate" %>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>验证用户名是否存在</title>
<script type="text/javascript">
var xmlHttp;
function createXMLHttpRequest()
{
if(window.ActiveXObject)
{
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}
else if(window.XMLHttpRequest)
{
xmlHttp = new XMLHttpRequest();
}
}
//处理方法
function CheckUserName()
{
createXMLHttpRequest();
var url= "LoginValidate.ashx?username="+document.getElementById("username").value;
xmlHttp.open("GET",url,true);
xmlHttp.onreadystatechange=ShowResult;
xmlHttp.send(null);
//document.getElementById("Msg").innerHTML='''';
}
//回调方法
function ShowResult()
{
if(xmlHttp.readyState==4)
{
if(xmlHttp.status==200)
{
document.getElementById("Msg").innerHTML=xmlHttp.responseText;
}
}
}
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<table style="width: 487px">
<tr>
<td style="width: 70px">
用户名：</td>
<td style="width: 231px"><input id="username" type="text" />
<input id="Button1" type="button" value="button" onclick="CheckUserName();" /></td>
<td id="Msg"></td>
</tr>
<tr>
<td style="width: 70px">
</td>
<td style="width: 231px">
</td>
<td>
</td>
</tr>
</table>
</div>
</form>
</body>
</html>
服务器端代码如下:(这里我是用的临时处理文件.ashx)
LoginValidate.ashx
<%@ WebHandler Language="C#" Class="LoginValidate" %>
using System;
using System.Web;
using System.Data;
using System.Data.SqlClient;
public class LoginValidate : IHttpHandler
{
public void ProcessRequest (HttpContext context)
{
context.Response.ContentType = "text/plain";
string username = context.Request.QueryString["username"].ToString();
string strSQL = "select username from users where username=''" + username + "''";
if (ReDataSet(strSQL).Tables[0].Rows.Count > 0)
{
context.Response.Write("该用户已经有人使用！");
}
else
{
context.Response.Write("恭喜你！"+username+"可以使用！");
}
System.Threading.Thread.Sleep(3000);
}
//数据库连接字符串
public static string strCon = "Data Source=.;database=exam;uid=sa;pwd=;";
/// <summary>
/// 执行SQL语句，返回DataSet
/// </summary>
/// <param name="strSQL"></param>
/// <returns></returns>
public DataSet ReDataSet(string strSQL)
{
SqlConnection con = new SqlConnection(strCon);
try
{
con.Open();
SqlDataAdapter da = new SqlDataAdapter(strSQL, con);
DataSet ds = new DataSet();
da.Fill(ds);
return ds;
}
catch (Exception ex)
{
throw new Exception(ex.Message);
}
finally
{
con.Close();
}
}
/// <summary>
/// 不重复调用
/// </summary>
public bool IsReusable
{
get
{
return false;
}
}
}
