private void bntBookRoom_Click(object sender, EventArgs e)
        {
            var ac_r = new Account_Room(DateTime.Parse(txbTime.Text), room.ID, Constants.userID);

            ac_r.PayStatus = Constants.BILL_TYPE.UNPAY;
            Account_RoomDAO.instance.AddAccount_Room(ac_r);
            room.RoomStatus = Constants.ROOM_STATUS.FULL;
            RoomDAO.Instance.UpdateRoom(room);
            this.Close();
        }
        private void bntCancel_Click(object sender, EventArgs e)
        {
            var ac_r = new Account_Room(DateTime.Parse(dateTimePicker_Date.Value.ToString("MM/dd/yyyy")), room.ID, Constants.userID);

            ac_r.PayStatus = Constants.BILL_TYPE.UNPAY;
            Account_RoomDAO.instance.AddAccount_Room(ac_r);
            room.RoomStatus = Constants.ROOM_STATUS.DATE;
            RoomDAO.Instance.UpdateRoom(room);
            this.Close();
        }