title: How can I get this DataTrigger to work?
body: <p>I want my TextBox to have a <strong>red background</strong> if the ViewModel property = "<strong>invalid</strong>". What do I have to change so this works?</p>
  
  <p>This version tells me that <strong>Background does not have a qualifying type name</strong>.</p>
  
  <pre><code>&lt;TextBox
      Width="200"
      Text="{Binding FieldEmail, UpdateSourceTrigger=PropertyChanged}"&gt;
      &lt;TextBox.Triggers&gt;
          &lt;DataTrigger Binding="{Binding FieldEmailValidationStatus}" Value="invalid"&gt;
              &lt;Setter Property="TextBox.Background" Value="Tomato"/&gt;
          &lt;/DataTrigger&gt;
      &lt;/TextBox.Triggers&gt;
  &lt;/TextBox&gt;
  </code></pre>
  
  <p>When I add "TextBox." it tells me I <strong>have to have an EventTrigger</strong>:</p>
  
  <pre><code>&lt;TextBox
      Width="200"
      Text="{Binding FieldEmail, UpdateSourceTrigger=PropertyChanged}"&gt;
      &lt;TextBox.Triggers&gt;
          &lt;DataTrigger Binding="{Binding FieldEmailValidationStatus}" Value="invalid"&gt;
              &lt;Setter Property="Background" Value="Tomato"/&gt;
          &lt;/DataTrigger&gt;
      &lt;/TextBox.Triggers&gt;
  &lt;/TextBox&gt;
  </code></pre>