private void BtnSave_Click(object sender, RoutedEventArgs e) { if (_upDownAmount.Value == null || _upDownPrice.Value == null) { return; } var item = new InvoiceItem { Name = _tbName.Text, Price = _upDownPrice.Value.Value, Amount = _upDownAmount.Value.Value, Currency = _currency, Unit = _cbUnit.SelectedItem as UnitOfMeasure }; item.SetTotal(); var result = Saver.Checker(item); if (result) { _items.Add(item); Init(); } }