private async void Cb_customer_SelectionChanged(object sender, SelectionChangedEventArgs e) {//select customer try { if (cb_customer.SelectedIndex != -1) { cb_package.IsEnabled = true; cb_period.IsEnabled = true; if (MainWindow.userLogin.type != "ag") { try { await FillCombo.fillPackageByCustomer(cb_package, (int)cb_customer.SelectedValue); cb_package.SelectedValue = oldPackageId; } catch { } } else { await FillCombo.fillAgentPackage(cb_package, MainWindow.userLogin.userId); } } } catch (Exception ex) { HelpClass.ExceptionMessage(ex, this); } }