title: WPF : How to animate element width whenever it changes
body: <p>This should be easy but I'm blanking out here.</p>
  
  <p>I have a <code>TextBlock</code> inside of a <code>Border</code> control. The <code>Width</code> of the <code>Border</code> changes based on the length of the text in the <code>TextBlock</code> (updated in ViewModel). I would like this change in <code>Width</code> to be animated so that the width grows slowly (instead of jerky). </p>
  
  <p>My Xaml:</p>
  
  <pre><code>&lt;Border x:Name="myBorder" BorderBrush="Black" BorderThickness="1" HorizontalAlignment="Left" VerticalAlignment="Top"&gt;
      &lt;TextBlock x:Name="myTextBlock" HorizontalAlignment="Left" Text="Some Text"/&gt;
  &lt;/Border&gt;
  </code></pre>