//đã xong private void tsmiSell_Click(object sender, EventArgs e) { int _maHoaDon = _MaHoaDonHienTai++; Staff _nhanVien = StaffDAO.Instance.LayNhanVienTheoMa(_Account.MaNV); FSell _fSell = new FSell(_maHoaDon, _nhanVien, this); _fSell.Show(); }