title: AppBarButton.Icon doesn't change on runtime
body: <p>I have a problem updating AppBarButton Icon on runtime depending on some conditions.</p>
  
  <pre><code>&lt;AppBarButton x:Name="WeekButton" Click="OnClick" Label="SomeText"
  
  &lt;/AppBarButton&gt;
  </code></pre>
  
  <p>I'm trying to update Icon property in some code behind with this code</p>
  
  <pre><code>WeekButton.Icon = new FontIcon() { Glyph = Runtime_Value_Here};
  </code></pre>
  
  <p>But nothing happens. The button doesn't change. But in any random time when the code works, It MAY change the button. I always see, that the Icon is new in code, but not on screen. None of the UpdateLayout helps.
  Would appreciate any help.
  Thanks</p>
  
  <p><strong>UPDATE:</strong>
  It seems to not working with FontIcon, as with BitmapIcon changing everything works fine.</p>