private void TaoMaHoaDon(DateTime ngayLap)
{
Object obj = bd.LayMaHDMax(ref err, ngayLap);
if (obj != null)
{
maHD = string.Format("{0}{1:00}{2:00}{3:000}", dtpNgayLap.Value.Year.ToString().Substring(2, 2).Trim(), dtpNgayLap.Value.Month, dtpNgayLap.Value.Day, Convert.ToInt32(obj));
lblMaHoaDon.Text = maHD;
}
}