使用jQuery和一般处理程序即时验证用户录入的学号是否重复，当光标离开输入框即给出提示。
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="AddStudent.aspx.cs" Inherits="AddStudent" %>
<!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>
<style type="text/css">
.clsShow
{
font-size: 13px;
border: solid 1px #cc3300;
padding: 2px;
display: none;
margin-bottom: 5px;
background-color: #ffe0a3;
}
</style>
<script type="text/javascript" src="Scripts/jquery-1.4.2.js"></script>
<script type="text/javascript">
$(function () {
$("#btnSave").click(function () {
if ($(".clsShow").html().toString() != "")//存在提示信息，则不允许提交表单
return false;
else
return true;
});
$("#txtNum").focus(); //输入焦点
$("#txtNum").keydown(function (event) {
if (event.which == "13") {//回车键,移动光标到密码框
$("#txtName").focus();
$("#txtNum").trigger("blur");
}
});
$("#txtNum").blur(function () {
//获取学号
var strTxtName = encodeURI($("#txtNum").val());
//开始发送数据
$.ajax
({ //请求验证学号是否重复
url: "Check.ashx",
type: "post",
//传送请求数据
data: { txtNum: strTxtName },
success: function (strValue) { //登录成功后返回的数据
//根据返回值进行状态显示
if (strValue == "True") {//注意是True,不是true
$(".clsShow").css("display", "inline");
$(".clsShow").html("学号已存在，请修改！");
}
else {
$(".clsShow").hide(); //就是把display属性变成none
$(".clsShow").html("");
}
}
})
})
})
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
学号:<asp:TextBox
ID="txtNum" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"
ControlToValidate="txtNum" ErrorMessage="不能为空"></asp:RequiredFieldValidator>
<div class="clsShow"></div>
<br />
姓名:<asp:TextBox ID="txtName" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server"
ControlToValidate="txtName" ErrorMessage="不能为空"></asp:RequiredFieldValidator>
<br />
数学:<asp:TextBox
ID="txtMath" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator3" runat="server"
ControlToValidate="txtMath" ErrorMessage="不能为空"></asp:RequiredFieldValidator>
<asp:RangeValidator ID="RangeValidator1" runat="server"
ControlToValidate="txtMath" ErrorMessage="分数在0-100之间" MaximumValue="100"
MinimumValue="0" Type="Integer"></asp:RangeValidator>
<br />
英语:<asp:TextBox ID="txtEnglish" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator4" runat="server"
ControlToValidate="txtEnglish" ErrorMessage="不能为空"></asp:RequiredFieldValidator>
<asp:RangeValidator ID="RangeValidator2" runat="server"
ControlToValidate="txtEnglish" ErrorMessage="分数在0-100之间" MaximumValue="100"
MinimumValue="0" Type="Integer"></asp:RangeValidator>
<br />
语文:<asp:TextBox ID="txtChinese" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator5" runat="server"
ControlToValidate="txtChinese" ErrorMessage="不能为空"></asp:RequiredFieldValidator>
<asp:RangeValidator ID="RangeValidator3" runat="server"
ControlToValidate="txtChinese" ErrorMessage="分数在0-100之间" MaximumValue="100"
MinimumValue="0" Type="Integer"></asp:RangeValidator>
<br />
<asp:Button ID="btnSave" runat="server" Text="保存" onclick="btnSave_Click" />
<asp:Button ID="btnBack" runat="server" Text="返回" CausesValidation="False"
onclick="btnBack_Click" />
<asp:Label ID="lblMsg" runat="server"></asp:Label>
</div>
</form>
</body>
</html>
一般处理程序Check.ashx代码：
<%@ WebHandler Language="C#" class="Check" %>
using System;
using System.Web;
public class Check : IHttpHandler {
public void ProcessRequest (HttpContext context) {
context.Response.ContentType = "text/plain";
string num = context.Request["txtNum"].ToString();
bool result = false;
if(num=="12")//为了简化代码，没有访问数据库。实际项目应查询数据库。
{
result = true;
}
context.Response.Write(result);
}
public bool IsReusable {
get {
return false;
}
}
}