private void LbLogin_MouseDown(object sender, MouseButtonEventArgs e)
        {
            //MessageBox.Show("登陆");
            using (SqlConnection conn = new SqlConnection(@"Data Source=192.168.1.130; Initial Catalog=HealthCard;User ID=sa;Password=stevev"))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    //1.执行非查询语句
                    //cmd.CommandText = "Insert into T_Users(U_UserName,U_Password,U_Name) values('test','test','test')";
                    //cmd.ExecuteNonQuery();

                    ////2.ExecuteScalar()获得插入的自增字段值
                    //cmd.CommandText = "insert into T_Users(U_UserName,U_Password) output inserted.U_ID values('test','test')";
                    ////cmd.ExecuteScalar()用于只有一行一列的返回值获取。
                    //long i = (long)cmd.ExecuteScalar();
                    //MessageBox.Show(i.ToString());

                    ////3.SqlDataReader()查询多条语句结果。
                    //cmd.CommandText = "select * from T_Users";
                    //using (SqlDataReader reader = cmd.ExecuteReader())
                    //{
                    //    while (reader.Read())
                    //    {
                    //        string name=reader.GetString(1);
                    //        MessageBox.Show(name);
                    //    }
                    //}

                    ////4.参数化查询避免注入
                    ////当仅仅是用sql语句做拼接字符串的，输入1'or'1'='1 会显示出所有数据。
                    //cmd.CommandText = "select U_ID from T_Users where U_UserName=@name";
                    //cmd.Parameters.Add(new SqlParameter("@name", TbUserName.Text));
                    //using (SqlDataReader reader = cmd.ExecuteReader())
                    //{
                    //    while (reader.Read())
                    //    {
                    //        long ID = reader.GetInt64(0);
                    //        MessageBox.Show(ID.ToString());
                    //    }
                    //}

                    //5.DataSet离线数据集-优点：降低服务器压力，编程也简单了。但数据量大对客户端内存压力大。

                    cmd.CommandText = "select * from T_Users";
                    //SqlDateAdapter是一个帮助我们把SqlCommand查询结果填充到DataSet中的类
                    SqlDataAdapter adapter =new SqlDataAdapter(cmd);
                    //DataSet相当于本地的数据集合
                    DataSet dataset =new DataSet();
                    //把SqlCommand查询结果填充到DataSet
                    adapter.Fill(dataset);

                    DataTable table=dataset.Tables[0];
                    DataRowCollection rows=table.Rows;
                    for(int i =0;i<rows.Count;i++)
                    {
                    DataRow row = rows[i];
                    long ID = (long)row["U_ID"];
                    string name = (string)row["U_UserName"];
                    MessageBox.Show(ID + "," + name);

                    }

 

 

 

                }
            }

 

            //MessageBox.Show("添加成功！");
        }