title: WPF: ListView: Display a default value instead of an empty string
body: <p>I have a Listview that's ItemSource is bound to a ObservableCollection and that's SelectedItem is bound to a string. It is possible that the observable collection contains an empty string; in that case, I want the listview to display some special string instead of just an empty item without text.</p>
  
  <p>This is how I imagine it should work:</p>
  
  <pre><code>&lt;ListView ItemSource="{Binding AvailableTags}" SelectedItem="{Binding SelectedTag}"&gt;
  &lt;ListView.ItemContainerStyle&gt;
       &lt;Style TargetType="ListViewItem"&gt;
            &lt;Setter Property="Content" Value="Untagged" /&gt;
                &lt;Style.Triggers&gt;
                     &lt;DataTrigger Binding="-&gt; Which binding to use?" Value=""&gt;
                         &lt;Setter Property="Content" Value="-&gt; How to get the Default value?" /&gt;
                     &lt;/DataTrigger&gt;
                &lt;/Style.Triggers&gt;
       &lt;/Style&gt;
  &lt;/ListView.ItemContainerStyle&gt;
  &lt;/ListView&gt;
  </code></pre>
  
  <p>As you can see, in this dummy source code, there are two place holders. How can I make it working? Or am I on the wrong track?</p>