webform1.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="test4_2.WebForm1" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
用户名:<asp:TextBox ID="txtName" runat="server" AutoPostBack="True" OnTextChanged="txtName_TextChanged"></asp:TextBox>
<asp:Label ID="lblValidate" runat="server"></asp:Label><br />
密码:<asp:TextBox ID="txtPassword" runat="server" TextMode="Password"></asp:TextBox><br />
E-mail:<asp:TextBox ID="txtMail" runat="server" TextMode="Email"></asp:TextBox><br />
<asp:Button ID="btnSubmit" runat="server" Text="确认" />
</div>
</form>
</body>
</html>
webform1.aspx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace test4_2
{
public partial class WebForm1 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
txtName.Focus();
}
protected void txtName_TextChanged(object sender, EventArgs e)
{
if (txtName.Text == "admin")
{
lblValidate.Text = "此用户已存在";
}
else
{
lblValidate.Text = "用户名可用";
}
}
}
}