ASP.NET 登录界面

//default.aspx.cs
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Data.OleDb;
using System.Data.SqlClient;
using System.Runtime.InteropServices;
using System.Configuration;
using System.Web.UI.WebControls;
using System.Web.Services.Description;
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
Button4.Attributes.Add("onclick", "window.open('Register.aspx')");//通过button4打开链接
string strConnection = ConfigurationManager.AppSettings["Str.Properties.Settings.masterConnectionString"].ToString();
SqlConnection objConnection = new SqlConnection(strConnection);
objConnection.Open();
SqlCommand cmd = new SqlCommand("select * from judging where name='" + TextBox1.Text.Trim() + "'", objConnection);
string sql = "select * from judging where name='" + TextBox1.Text + "'and password='" + TextBox2.Text + "'";
cmd.CommandText = sql;
/*
***********************************************************************************************
*判断是否有此ID,ExecuteScalar() return the first column of the first row in the result set.
*/
if (cmd.ExecuteScalar() == null)//无此用户
{
Label1.Text = "Sorry, please check your id and psw";
Button3.Visible = false;
}
else
{
Label1.Text ="Welcome to "+TextBox1.Text;
Button3.Visible = true;
}

}
protected void Button1_Click(object sender, EventArgs e)
{
Panel1.Visible = false;
Panel2.Visible = true;
}
protected void Button4_Click(object sender, EventArgs e)
{

}
protected void Button3_Click(object sender, EventArgs e)