Recognizing checkbox created by a template in a fired event

I've created an unfoldable list of checkboxes like so.

<Expander x:Name=...>
  <ListBox ItemsSource="{x:Static local:MainWindow.AllTypes}">
    <ListBox.ItemTemplate>
      <DataTemplate>
        <CheckBox Content="{Binding Name}"
                  Checked="ToggleButton_OnToggled"
                  Unchecked="ToggleButton_OnToggled"/>
      </DataTemplate>
    </ListBox.ItemTemplate>
  </ListBox>
</Expander>

I also have a method with the signature below.

private void FilterStuffOut(String condition)
{
  CollectionViewSource source 
    = new CollectionViewSource { Source = dataGrid.ItemsSource };
  ICollectionView view = source.View;
  view.Filter = element => BringItOut(element, condition);
  dataGrid.ItemsSource = view;
}

I'm unsure (and poking around with intellisense both in sender and eventArgs gave me nothing) how to get to know which checkbox is the firey one. Where should I look for it in the method below?

private void ToggleButton_OnToggled(
  Object sender, RoutedEventArgs eventArgs) { ... }