title: Override ThemeResource for specific controls
body: <p>I want to create a transparent TextBox, with no background color when focused (default is white, or <code>SystemControlBackgroundChromeWhiteBrush</code>).
  I understand that I can override the used color in the App.xaml like so:</p>
  
  <pre><code>&lt;Application.Resources&gt;
      &lt;SolidColorBrush x:Key="SystemControlBackgroundChromeWhiteBrush"&gt;Transparent&lt;/SolidColorBrush&gt;
  &lt;/Application.Resources&gt;
  </code></pre>
  
  <p>(or by using multiple ThemeDictionaries)</p>
  
  <p>However I don't want to modify ALL TextBlocks but only specific ones. My first guess was to include the changed brush in the TextBlock's Resources, but this doesn't work.</p>