title: Change appearance of WPF DatePicker's textbox
body: <p>Changing the Foreground property of the WPF DatePicker does change the colour of the text in the text box, but changing the Background property doesn't. But you can change it by styling the contained DatePickerTextBox.  So I ended up with this:</p>
  
  <pre><code>&lt;DatePicker Foreground="Yellow" &gt;
      &lt;DatePicker.Resources&gt;
          &lt;Style TargetType="{x:Type DatePickerTextBox}" &gt;
              &lt;Setter Property="Background" Value="Black" /&gt;
          &lt;/Style&gt;
      &lt;/DatePicker.Resources&gt;
  &lt;/DatePicker&gt;
  </code></pre>
  
  <p>Is there a tidier way of doing this without templating the whole control? 
  Is there a way to just template the named part i.e. PART_TextBox?</p>