public static bool NhanBaoHanh(SAN_PHAM sp)
        {
            LICH_SU_SAN_PHAM lssp = new LICH_SU_SAN_PHAM(sp, Init.nhanVien.MSNV, 5, sp.TRANG_THAI + " -> 1");

            LICH_SU_SAN_PHAM.insert(lssp);
            return(true);
        }
        public static bool ThemSanPham(SAN_PHAM sp, string ghiChu)
        {
            LICH_SU_SAN_PHAM lssp = new LICH_SU_SAN_PHAM(sp, Init.nhanVien.MSNV, 0, "Add Product " + ghiChu);

            LICH_SU_SAN_PHAM.insert(lssp);
            return(true);
        }
        public static bool ThanhToan(SAN_PHAM cu, SAN_PHAM moi)
        {
            List <LICH_SU_SAN_PHAM> log = new List <LICH_SU_SAN_PHAM>();

            if (cu.MA_CHI_TIET_SAN_PHAM != moi.MA_CHI_TIET_SAN_PHAM)
            {
                log.Add(new LICH_SU_SAN_PHAM(cu, Init.nhanVien.MSNV, 2, cu.MA_CHI_TIET_SAN_PHAM + " -> " + moi.MA_CHI_TIET_SAN_PHAM));
            }
            if (cu.NGAY_BAT_DAU_BAO_HANH != moi.NGAY_BAT_DAU_BAO_HANH)
            {
                log.Add(new LICH_SU_SAN_PHAM(cu, Init.nhanVien.MSNV, 3, (cu.NGAY_BAT_DAU_BAO_HANH != null? cu.NGAY_BAT_DAU_BAO_HANH.ToString():"") + " -> " + moi.NGAY_BAT_DAU_BAO_HANH));
            }
            if (cu.NGAY_KET_THUC_BAO_HANH != moi.NGAY_KET_THUC_BAO_HANH)
            {
                log.Add(new LICH_SU_SAN_PHAM(cu, Init.nhanVien.MSNV, 4, (cu.NGAY_KET_THUC_BAO_HANH != null ? cu.NGAY_KET_THUC_BAO_HANH.ToString() : "") + " -> " + moi.NGAY_KET_THUC_BAO_HANH));
            }
            if (cu.TRANG_THAI != moi.TRANG_THAI)
            {
                log.Add(new LICH_SU_SAN_PHAM(cu, Init.nhanVien.MSNV, 5, cu.TRANG_THAI + " -> " + moi.TRANG_THAI));
            }
            if (cu.GIA_MUA != moi.GIA_MUA)
            {
                log.Add(new LICH_SU_SAN_PHAM(cu, Init.nhanVien.MSNV, 6, cu.GIA_MUA + " -> " + moi.GIA_MUA));
            }
            if (cu.GIA_BAN != moi.GIA_BAN)
            {
                log.Add(new LICH_SU_SAN_PHAM(cu, Init.nhanVien.MSNV, 7, cu.GIA_BAN + " -> " + moi.GIA_BAN));
            }
            if (cu.GHI_CHU != moi.GHI_CHU)
            {
                log.Add(new LICH_SU_SAN_PHAM(cu, Init.nhanVien.MSNV, 8, cu.GHI_CHU + " -> " + moi.GHI_CHU));
            }
            moi.IMEI = cu.IMEI;
            try
            {
                for (int i = 0; i < log.Count; i++)
                {
                    LICH_SU_SAN_PHAM.insert(log[i]);
                }
                return(true);
            }
            catch (Exception)
            {
                return(false);
            }
        }