public List <ActiveUser> GetActiveUser()
 {
     using (SqlConnection connection = new SqlConnection(connectionString))
     {
         List <ActiveUser> ActiveUserList = new List <ActiveUser>();
         SqlCommand        command        = new SqlCommand();
         command.CommandText = "select * from ActiveSession;";
         command.Connection  = connection;
         connection.Open();
         SqlDataReader reader = command.ExecuteReader();
         while (reader.Read())
         {
             ActiveUser Active_User = new ActiveUser();
             Active_User.CardNumber   = reader["CardNumber"].ToString();
             Active_User.PcName       = reader["PcName"].ToString();
             Active_User.StartingTime = Convert.ToDateTime(reader["StartingTime"]);
             ActiveUserList.Add(Active_User);
         }
         return(ActiveUserList);
     }
 }
        public List<ActiveUser> GetActiveUser()
        {
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                List<ActiveUser> ActiveUserList = new List<ActiveUser>();
                SqlCommand command = new SqlCommand();
                command.CommandText = "select * from ActiveSession;";
                command.Connection = connection;
                connection.Open();
                SqlDataReader reader = command.ExecuteReader();
                while (reader.Read())
                {
                    ActiveUser Active_User = new ActiveUser();
                    Active_User.CardNumber = reader["CardNumber"].ToString();
                    Active_User.PcName = reader["PcName"].ToString();
                    Active_User.StartingTime = Convert.ToDateTime(reader["StartingTime"]);
                    ActiveUserList.Add(Active_User);
                }
                return ActiveUserList;

            }
        }