var itemSlipsManager = new ItemSlipsManager(OAuth2);
 var slips = new ItemSlips
 {
 FaturaTip = JTFaturaTip.ftSFat,
 SeriliHesapla = false,
 KayitliNumaraOtomatikGuncellensin = false,
 FatUst = new ItemSlipsHeader
 {
 FATIRS_NO = invoiceNumber.DocumentNumber,
 GIB_FATIRS_NO = invoiceNumber.GibDocumentNumber,
 CariKod = SystemSettings.DefaultAccountCode,
 Tarih = DateTime.Now,
 TIPI = JTFaturaTipi.ft_Kapali,
 KDV_DAHILMI = false,
 Tip = JTFaturaTip.ftSFat,
 KS_KODU = client.CashCode.ToString("####"),
 BRUTTUTAR = transactionHeader.GROSS_TOTAL.HasValue
 ? (double)transactionHeader.GROSS_TOTAL
 : 0,

 EfaturaCarisiMi = isEInvoice,

 KDV = (double?)transactionHeader.GROSS_VAT_TOTAL,
 FiiliTarih = transactionHeader.TRANS_DATE,
 GENELTOPLAM = (double?)transactionHeader.GROSS_TOTAL,
 GEN_ISK1T = (double?)transactionHeader.DISCOUNT_ON_TOTAL,

 MFAZ_ISKT = (double?)transactionHeader.DISCOUNT_ON_LINES
 },
 Kalems = new List<ItemSlipLines>()
 };
 foreach (var line in transactionSales)
 {
 slips.Kalems.Add(new ItemSlipLines
 {
 StokKodu = line.CODE,
 STra_NF = (double?)(line.UNIT_PRICE - line.VAT_TOTAL - line.CAMPAIGN_DISCOUNT -
 line.CHEQUE_DISCOUNT),
 STra_BF = (double?)line.UNIT_PRICE,
 DEPO_KODU = client.WarehouseCode,
 STra_GCMIK = line.AMOUNT,
 STra_DOVTIP = 0, 
 STra_DOVFIAT = (double?)line.CURRENCY_UNIT_PRICE,
 Sira = (int)line.LINE_NO,
 STra_SatIsk = (double?)line.CAMPAIGN_DISCOUNT,
 STra_SatIsk2 = (double?)line.CHEQUE_DISCOUNT,
 STra_ACIK = line.DESCRIPTION

 });
 }

 var result = itemSlipsManager.PostInternal(slips);