title: How to disable a ShellContent button
body: <p>I have a brand new Xamarin Shell application.  I just want to disable one of the buttons in the TabBar section.  I see there is an IsEnabled property but even if I set it to False, the button is still clickable and the view becomes visible.</p>
  <pre><code>&lt;TabBar&gt;
      &lt;ShellContent Title=&quot;Home&quot; Route=&quot;HomePage&quot; ContentTemplate=&quot;{DataTemplate local:HomePage}&quot;/&gt;
      &lt;ShellContent Title=&quot;Settings&quot; Route=&quot;SettingsPage&quot; ContentTemplate=&quot;{DataTemplate local:SettingsPage}&quot; IsEnabled=&quot;False&quot; /&gt;
  &lt;/TabBar&gt;
  </code></pre>
  <p>Is it not possible to disable the buttons that appear in the lower navigation of a Xamarin.Forms application?  I was hoping to disable certain buttons when conditions weren't met and enable them using event listeners.</p>