public List<InvoiceFindResult> CollectInvoices(string filter)
        {
            InvoiceApi api = new InvoiceApi(site, company, username, password, cookie);

            List<InvoiceFindResult> results = api.FindInvoices(filter, "Id", null, null, null, returnFields);
            logger.Info("Found " + results.Count + " invoices");
            return results;
        }
        public List <InvoiceFindResult> CollectInvoices(string filter)
        {
            InvoiceApi api = new InvoiceApi(site, company, username, password, cookie);

            List <InvoiceFindResult> results = api.FindInvoices(filter, "Id", null, null, null, returnFields);

            logger.Info("Found " + results.Count + " invoices");
            return(results);
        }