title: BindableProperty in ContentView not working
body: <p>I made a very simple Yes/No RadioBox control.</p>
  
  <p>In it's code behind I have the following <code>BindableProperty</code>:</p>
  
  <pre><code>    public static readonly BindableProperty SelectedValueProperty = BindableProperty.Create(
          "SelectedValue",
          typeof(int),
          typeof(YesNoView),
          0,
          BindingMode.TwoWay);
  </code></pre>
  
  <p>And it's property:</p>
  
  <pre><code>    public int SelectedValue
      {
          get { return (int) GetValue(SelectedValueProperty); }
          set { SetValue(SelectedValueProperty, value); }
      }
  </code></pre>
  
  <p>This property is bound in the ContentView-XAML using something like this:</p>
  
  <pre><code>          &lt;DataTrigger Binding="{Binding SelectedValue}" Value="0" TargetType="Image"&gt;
              &lt;Setter Property="Source" Value="radiobutton_checked.png" /&gt;
            &lt;/DataTrigger&gt;
  </code></pre>
  
  <p>Whenever I use my ContentView in some Page and set the <code>SelectedValue</code> to a constant value, everything works fine!</p>
  
  <p>However, when I use a <code>{Binding SomeValue}</code> instead of a constant value, where <code>SomeValue</code> is a property (with notify) on the Page I'm using the ContentView on, it will simply refuse to do anything. Whenever I set <code>SomeValue</code> to some value, it never reaches the ContentView and it's driving me insane why it isn't working.</p>
  
  <p>Even when I adjust the BindableProperty to also specify a propertyChanged event, it is simply never triggered unless I revert back to a constant value in the Xaml, rather than a binding.</p>
  
  <p>Could anyone shed a light as to why this is happening and not working as I would expect?</p>
  
  <p>EDIT: I should add that in both the Page and the View the BindingContext is set to this.</p>