private void buttonEditQuantity_Click(object sender, RoutedEventArgs e) { FormattedListBoxItem selectedItem = listBoxIncludedItems.SelectedItem as FormattedListBoxItem; if (selectedItem == null) { return; } ItemGroup itemGroup = selectedItem.ReferenceObject as ItemGroup; if (itemGroup == null) { return; } int?newQuantity = PosDialogWindow.PromptNumber(Strings.ItemEditorEditQuantity, null); if (newQuantity.HasValue) { itemGroup.SetTargetItemQuantity(newQuantity.Value); if (EditQuantityNeedsUpdating(itemGroup)) { _itemGroupsNeedingUpdate.Add(itemGroup); } InitializeListBoxes(); DoValueChangedEvent(); } }