title: TextBlock style triggers
body: <p>I would like to combine the DisplayNames from two different ViewModels, but only IF the first is not equal to a NullObject.</p>
  <p>I <em>could</em> easily do this in either a converter or a parent view model, but am</p>
  <p>This displays nothing at all:</p>
  <pre><code>        &lt;TextBlock Grid.Column=&quot;2&quot; Grid.Row=&quot;0&quot; &gt;
              &lt;TextBlock.Inlines&gt;
                  &lt;Run Text=&quot;{Binding HonorificVm.DisplayName}&quot;/&gt;
                  &lt;Run Text=&quot;{Binding PersonNameVm.DisplayName}&quot;/&gt;
              &lt;/TextBlock.Inlines&gt;
              &lt;TextBlock.Style&gt;
                  &lt;Style TargetType=&quot;{x:Type TextBlock}&quot;&gt;
                      &lt;Style.Triggers&gt;
                          &lt;DataTrigger Binding=&quot;{Binding HonorificVm.Honorific}&quot; Value=&quot;{x:Static model:Honorific.NullHonorific}&quot;&gt;
                              &lt;Setter Property=&quot;Text&quot; Value=&quot;PersonNameVm.DisplayName&quot;/&gt;
                          &lt;/DataTrigger&gt;
                      &lt;/Style.Triggers&gt;
                  &lt;/Style&gt;
              &lt;/TextBlock.Style&gt;
          &lt;/TextBlock&gt;
  </code></pre>
  <p>Why?</p>