title: Binding textblock value doesn't change after changing binded value
body: <p>Why does TextBlock "T1" not show "101" after clicking on Button "B1" and still shows "100"?</p>
  
  <pre><code>&lt;StackPanel&gt;
      &lt;TextBlock Name="T1" Text="{x:Bind value, Mode=OneWay}"/&gt;
      &lt;Button Name="B1" Content="+1" Click="B1_Click"/&gt;
  &lt;/StackPanel&gt;
  </code></pre>
  
  <p>and</p>
  
  <pre><code>public sealed partial class MainPage : Page
  {
      public int value;
      public MainPage()
      {
          InitializeComponent();
          value = 100; // initial value
      }
      private void B1_Click(object sender, Windows.UI.Xaml.RoutedEventArgs e)
      {
          value = value + 1;
      }
  }
  </code></pre>