Question

I am only displaying the selected element of a ListBox (yeah I know) … And I am trying to understand why if I have a single ListBox.ItemTemplate with a single child of ListBoxItem, I have to traverse 2 ListBoxItems to access the element named “thisListBoxItem”? It seems like there should only be one visual ListBoxItem element.

my XAML

<ListBox Name="cjisDisplayItemListBox" SelectionChanged="cjisDisplayItemListBox_SelectionChanged_1">
  <ListBox.ItemTemplate >
    <DataTemplate>
      <ListBoxItem Name="thisListBoxItem" Visibility="Collapsed">
      <!-- some TextBlocks with bindings here --> 
      </ListBoxItem>
    </DataTemplate>
  </ListBox.ItemTemplate>
</ListBox>

//First I cast SelectedItem to a ListBoxItem (myListBoxItem)
// then I have to descend to a lower ListBoxItem via the FindName property..

private void cjisDisplayItemListBox_SelectionChanged_1(object sender, SelectionChangedEventArgs e)
                    {
                        ListBox lb = sender as ListBox;
                        object item = lb.SelectedItem as object;
                        ListBoxItem myListBoxItem = (ListBoxItem)(lb.ItemContainerGenerator.ContainerFromItem(item));
                        ContentPresenter myContentPresenter = FindVisualChild<ContentPresenter>(myListBoxItem);
                        if (myContentPresenter == null) return;
                        DataTemplate myDataTemplate = myContentPresenter.ContentTemplate;
                        ListBoxItem temp = (ListBoxItem)myDataTemplate.FindName("thisListBoxItem", myContentPresenter);
                        if (myListBoxItem.IsSelected) temp.Visibility = System.Windows.Visibility.Visible;
                    }

Answer 1

What you have is incorrect. The ListBox will automatically wrap the items in instances of ListBoxItem. In your case, you are displaying a ListBoxItem (from your DataTemplate) in the one that is automatically created for you.

You should use ItemContainerStyle to set properties on the automatically created ListBoxItem.