public override string ToStringFile()
        {
            string s = ", ";

            return(Maso.PadRight(7, ' ') + s + loai.PadRight(10, ' ') + s + Ten.PadRight(23, ' ') + s + NgayGio.ToString(formatXuat).PadRight(24, ' ')
                   + s + DiaDiem.PadRight(10, ' ') + s + DienGia.PadRight(10, ' ') + s + SoLuong);
        }
 public override string ToString()
 {
     return(Maso.PadRight(9, ' ') + loai.PadRight(12, ' ') + Ten.PadRight(25, ' ') + NgayGio.ToString(formatXuat).PadRight(26, ' ')
            + DiaDiem.PadRight(12, ' ') + ChuTri.PadRight(12, ' ') + ThoiLuong);
 }