title: Dependency property in User Control is null after assigning value
body: <p>I have a user control, has a Frame as a dependency property</p>
  
  <pre><code>public partial class NavigationBar : UserControl
  {
      public NavigationBar()
      {
          this.InitializeComponent();
      }
  
      public Frame NavigationFrame
      {
          get { return (Frame)GetValue(NavigationFrameProperty); }
          set { SetValue(NavigationFrameProperty, value); }
      }
  
      // Using a DependencyProperty as the backing store for NavigationFrame.  This enables animation, styling, binding, etc...
      public static readonly DependencyProperty NavigationFrameProperty =
          DependencyProperty.Register("NavigationFrame", typeof(Frame), typeof(NavigationBar), new UIPropertyMetadata());
  }
  </code></pre>
  
  <p>Using the User Control code:</p>
  
  <pre><code>&lt;userControls:NavigationBar NavigationFrame="{Binding ElementName=masterPage, Path=frameNavigations}" /&gt;
  
   &lt;Frame x:Name="frameNavigations"/&gt;
  </code></pre>
  
  <p>Why the NavigationFrame dependency property still null after loading ?</p>
  
  <p>Thanks in advance</p>