title: WinUI 3.0 Desktop: Background color of TextBox gets changed on mouse over
body: <p>I have started to work with WinUI 3, the new UI tech from Microsoft.</p>
  <p>I have a <code>TextBox</code> that I want to set to readonly, i.e. <code>IsReadOnly=&quot;True&quot;</code> (Remark: The user shall still be able to copy content from it, that is why I do not want to set it to disabled, i.e. <code>IsEnabled=&quot;False&quot;</code>.)</p>
  <p>When setting it to <code>IsReadOnly=&quot;True&quot;</code> I noticed that the <code>TextBox</code> still keeps its default white background. I wanted to change this, in order to avoid having users clicking on it because they think that it is possible to change its content.</p>
  <p>I decided to set some kind of grayish color for the background:</p>
  <pre><code>    &lt;TextBox IsReadOnly=&quot;True&quot; Background=&quot;SlateGray&quot; Text=&quot;The content...&quot;&gt;&lt;/TextBox&gt;
  </code></pre>
  <p>This works as expected, but with one problem: <strong>As soon as the mouse hovers over the <code>TextBox</code> the background changes back to white</strong>. When the mouse is no longer over the <code>TextBox</code>, the color changes back to the specified gray background color.</p>
  <p>In WPF I would have tried some DataTrigger in order to keep the formatting, but there are no DataTriggers (yet?) in WinUI.</p>
  <p>I also tried setting other color related properties on the <code>TextBox</code> in order to see if they have anything todo with the mentioned behavior, but setting these did not change anything:</p>
  <pre><code>FocusVisualPrimaryBrush, FocusVisualSecondaryBrush, SelectionHighlightColor, SelectionHighlightColorWhenNotFocused
  </code></pre>
  <br>
  I am open for all kinds of suggestions on how to keep the background color when the mouse is over the readonly `TextBox`, thank you.