Altering existing Voucher creating new Voucher

[saivineeth100]

          As per your suggestion, I am retrieving voucher first. And then immediately posting same voucher without any modification, via PostVoucherAsync() method. Still Tally is creating new voucher, insteading of updating existing one.

voucher = await tally.GetVoucherAsync<TCM.Voucher>(_invoice.Tally_MasterId.ToString(), new TCM.VoucherRequestOptions()
                {
                    LookupField = TCM.VoucherLookupField.MasterId,
                    FetchList = TCM.Constants.Voucher.InvoiceViewFetchList.All
                });

                if (voucher != null)
                {
                    var resultVT = await tally.PostVoucherAsync<TCM.Voucher>(voucher);

                    if (resultVT.Status == TCM.RespStatus.Sucess)
                    {
                        var y = System.Text.RegularExpressions.Regex.Matches(resultVT.Response!, @"[0-9.]+")[0].Value;
                        _invoice.Tally_MasterId = int.Parse(y ?? "0");
                        _context.Invoices.Update(_invoice);
                        await _context.SaveChangesAsync();
                    }

                }

Originally posted by @drparasmehta in https://github.com/Accounting-Companion/TallyConnector/issues/5#issuecomment-1407551179