int invoiceRef = 1355;

UnityObjects.Data invoice = Global.UnityApp.NewDataObject(UnityObjects.DataObjectType.doSalesInvoice);
if (invoice.Read(invoiceRef))
{
UnityObjects.Lines invoiceLine = invoice.DataFields.FieldByName("TRANSACTIONS").Lines;
//invoiceLine[invoiceLine.Count - 1].FieldByName("QUANTITY").Value = 5; // faturadaki son satırı günceller

transactions_lines[0].FieldByName('XXXX').Value := XXXX; // ilk satır

transactions_lines[1].FieldByName('XXXX').Value := XXXX; // birinci satır

if (!invoice.Post())
{
MessageBox.Show("Güncellendi");