public async Task <List <Bill> > DeleteBillAsync(List <Bill> listBill) { List <Bill> result = new List <Bill>(); checkServiceCommunication(); List <Bill> gateWayResultList = await _gatewayOrder.DeleteBillAsync(listBill); if (gateWayResultList.Count == 0) { foreach (Bill bill in listBill) { int returnValue = _dataSet.DeleteBill(bill.ID); if (returnValue > 0) { result.Add(bill); } } } return(result); }