public static bool NhanBaoHanh(string imei)
        {
            SAN_PHAM sp = LaySanPham(imei);

            sp.TRANG_THAI = 1;
            LichSuSanPham.NhanBaoHanh(sp);
            SAN_PHAM.update(sp);
            return(true);
        }
 public static bool ThemSanPham(SAN_PHAM sp)
 {
     SAN_PHAM.insert(sp);
     LichSuSanPham.ThemSanPham(sp, sp.GHI_CHU);
     return(true);
 }