private async void PostSales()
        {
            List<Sale> sales = await SaleSaveInfo.GetSaleList();
            var arLiveApi = new HttpClientWebApi();

            foreach (Sale sale in sales)
            {
                sale.Id = Guid.NewGuid().ToString();
                await arLiveApi.PostSaleInvoice(sale);
            }

            SaleSaveInfo.ResetSavedSales();

            //pendingInvoiceCount.Text = "Pending Invoices: " + 0;
        }
        private async void btnSync_OnClick(object sender, RoutedEventArgs e)
        {
            btnSync.IsEnabled = false;
            CustomerDataGroup firstGroup = _customerDataGroups.FirstOrDefault();
            if (firstGroup != null) firstGroup.Items.Clear();
            var arLiveApi = new HttpClientWebApi();
            await arLiveApi.Refresh();

            PostSales();
            LoadCustomers();

            btnSync.IsEnabled = true;
        }