title: Change the focused border color of a Wpf textbox when it GotFocus()
body: <p>What I want: to change the border color to yellow when any textbox has focus.</p>
  
  <p>What I tried:</p>
  
  <pre><code>&lt;Window.Resources&gt;
      &lt;Style TargetType="TextBox"&gt;
          &lt;Style.Triggers&gt;
              &lt;Trigger Property="IsFocused" Value="True"&gt;
                  &lt;Setter Property="BorderBrush" Value="Yellow"&gt;&lt;/Setter&gt;
                  &lt;Setter Property="BorderThickness" Value="1"&gt;&lt;/Setter&gt;
              &lt;/Trigger&gt;
          &lt;/Style.Triggers&gt;
      &lt;/Style&gt;
  &lt;/Window.Resources&gt;
  </code></pre>
  
  <p>No joy. Cannot figure out why the border remains blue.
  This is similar, but not a duplicate of <a href="https://stackoverflow.com/questions/26601692/how-to-change-the-color-of-the-border-of-a-textbox-when-it-has-focus">How to change the color of the Border of a TextBox when it has focus?</a>.</p>