webform1.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="test5_7.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>
        <strong>登录</strong><br />
        用户名：<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
        <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ErrorMessage="用户名不能为空" ControlToValidate="TextBox1" Display="Dynamic" ForeColor="Red"></asp:RequiredFieldValidator>
        <br />
        密&nbsp;码：<asp:TextBox ID="TextBox2" runat="server" TextMode="Password"></asp:TextBox>
        <asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server" ErrorMessage="密码不能为空" Display="Dynamic" ControlToValidate="TextBox2" ForeColor="Red"></asp:RequiredFieldValidator>
        <br />
        <asp:Button ID="Button1" runat="server" Text="登录" OnClick="Button1_Click" /><br />
        <asp:Label ID="Label1" runat="server" Text=""></asp:Label>
    </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 test5_7
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            UnobtrusiveValidationMode = UnobtrusiveValidationMode.None;
        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            if (TextBox1.Text == "admin" && TextBox2.Text == "123")
            {
                Label1.Text = "登录成功";
            }
            else
            {
                Label1.Text = "输入的用户名或密码错误";
            }
        }
    }
}