protected void btnLogin_Click(object sender, EventArgs e)

        {

            try //这里做检测，是因为如果没有检测，连接错误后会把数据库里的内容显示在出错网页中

            {

                string username = txtUserName.Text.Trim(); //删除空白字符

                string pwd = txtPwd.Text.Trim();

                if (string.IsNullOrEmpty(username) || string.IsNullOrEmpty(pwd))

                {

                    //Response.Write("用户名或者密码不能为空");

                    Response.Write("<script>alert('用户名或者密码不能为空');</script>");

                }

                else

                {

                    //写Sql语句

                    string sSql = string.Format("select UserID from TestDB.dbo.UserInfor Where UserName='{0}' and Pwd='{1}'", username, pwd);

                    //数据库连接语句

                    //DataBase：要连接的数据库名称；  Server：服务器名称，'.'代表本机服务器，如果服务器在其他地方，这里输入IP地址

                    //Integrated Security: ture代表windows身份验证，登录名和密码就不需要了；false代表SQL Server身份验证

                    //Uid用户名；Password密码

                    //string connStr = "Database=TestDB;Server=.;Integrated Security=false;Uid=sa;Password=123;";

                    //读取配置文件中的数据库连接语句

                    string connStr = ConfigurationManager.ConnectionStrings["TestDB"].ToString();

                    //普通写法，需要自己释放资源

                    {

                        //和数据库建立连接，并打开连接

                        SqlConnection con = new SqlConnection(connStr);

                        con.Open();

                        //执行语句，要传两个参数，一个是SQL语句，一个是数据库连接类

                        SqlCommand cmd = new SqlCommand(sSql, con);

                        //把查询结果赋值给SqlDataReader对象

                        SqlDataReader read = cmd.ExecuteReader();

                        //查看是否有记录

                        if (read.HasRows)

                        {

                            Response.Redirect("UserInforM.aspx");

                        }

                        else

                        {

                            Response.Write("用户名或者密码错误");

                        }

                        //释放资源,并关闭

                        read.Dispose();

                        read.Close();

                        con.Dispose();

                        con.Close();

                    }

                    //用Using可以自动释放资源

                    {

                        using (SqlConnection con = new SqlConnection(connStr)) //自动释放con

                        {

                            con.Open();

                            SqlCommand cmd = new SqlCommand(sSql, con);

                            using (SqlDataReader read = cmd.ExecuteReader())  //自动释放read

                            {

                                if (read.HasRows)

                                {

                                    Response.Write("登录成功");

                                }

                                else

                                {

                                    Response.Write("用户名或者密码错误");

                                }

                            }

                        }

                    }

                }

            }

            catch (Exception ex)

            {

                Response.Write("网站正在维修中");

            }

        }

<connectionStrings>

    <add  name="TestDB" connectionString="Database=TestDB;Server=.;Integrated Security=false;Uid=sa;Password=123;" providerName="System.Data.SqlClient"/>

  </connectionStrings>

 public partial class UserInforM : System.Web.UI.Page

    {

        protected void Page_Load(object sender, EventArgs e)

        {

            try

            {

                string sSql = string.Format("select UserID,UserName,RealName,ClassName,Major from TestDB.dbo.UserInfor");

                string connStr = ConfigurationManager.ConnectionStrings["TestDB"].ToString();

                using (SqlConnection con = new SqlConnection(connStr)) //自动释放con

                {

                    con.Open();

                    SqlCommand cmd = new SqlCommand(sSql, con);

                    using (SqlDataReader read = cmd.ExecuteReader())  //自动释放read

                    {

                        GridView1.DataSource = read;

                        GridView1.DataBind();

                    }

                }

            }

            catch (Exception ex)

            {

                Response.Write("错误");

            }

        }

    }