title: Changing style based on trigger with Xamarin.Forms on WinPHone 8.1
body: <p>I have the following style</p>
  
  <pre><code>&lt;Style x:Key="GreenButtonStyle" BasedOn="{StaticResource MyButtonBaseStyle}" TargetType="Button"&gt;
      &lt;Style.Triggers&gt;
          &lt;Trigger TargetType="Button" Property="IsEnabled" Value="False"&gt;
              &lt;Setter Property="BackgroundColor" Value="Silver" /&gt;
              &lt;Setter Property="TextColor" Value="Black" /&gt;
          &lt;/Trigger&gt;
          &lt;Trigger TargetType="Button" Property="IsEnabled" Value="True"&gt;
              &lt;Setter Property="BackgroundColor" Value="Green" /&gt;
              &lt;Setter Property="TextColor" Value="Orange" /&gt;
          &lt;/Trigger&gt;
      &lt;/Style.Triggers&gt;
  &lt;/Style&gt;
  </code></pre>
  
  <p>Which I use in the following view.</p>
  
  <pre><code>&lt;Button x:Name="ConfirmButton" 
      Text="Confirm" 
      Style="{StaticResource GreenButtonStyle}" 
      IsEnabled="{Binding Source={x:Reference Some}, Path=ConfirmEnabled}"
      /&gt; 
  &lt;Button x:Name="ToggleButton"
      Text="Toggle" 
      Clicked="Toggle_Clicked"
      /&gt;
  </code></pre>
  
  <p>With the code behind (just snippets)</p>
  
  <pre><code>public partial class SomeView : ContentPage, INotifyPropertyChanged
  {
      public event PropertyChangedEventHandler PropertyChanged;
  
      private bool _confirmEnabled = false;
      public bool ConfirmEnabled
      {
          get { return _confirmEnabled; }
      }
  
      private void Toggle_Clicked(object sender, EventArgs e)
      {
          _confirmEnabled = !_confirmEnabled;
          PropertyChanged(this, new PropertyChangedEventArgs(nameof(ConfirmEnabled)));
      }
  }
  </code></pre>
  
  <p>When the View comes into play, everything is ok with the button inactive. When I click the toggle button, the font changes color to Orange as intended, but the background doesn't change color to green.</p>
  
  <p>If I click the toggle twice (disable then enable) the font is Orange and background is finally green.</p>
  
  <p>Anybody have any idea why the background color isn't changed on the first change of ConfirmEnabled to true?</p>