title: KeyBinding in UserControl doesn't work when TextBox has the focus
body: <p>The following situation. I've got a UserControl with five keybindings. When the TextBox has the focus the keybindings of the UserControl stop firing..</p>
  
  <p>Is there a way to fix this 'problem'?</p>
  
  <pre><code>&lt;UserControl.InputBindings&gt;
      &lt;KeyBinding Key="PageDown" Modifiers="Control" Command="{Binding NextCommand}"&gt;&lt;/KeyBinding&gt;
      &lt;KeyBinding Key="PageUp" Modifiers="Control" Command="{Binding PreviousCommand}"&gt;&lt;/KeyBinding&gt;
      &lt;KeyBinding Key="End" Modifiers="Control"  Command="{Binding LastCommand}"&gt;&lt;/KeyBinding&gt;
      &lt;KeyBinding Key="Home" Modifiers="Control" Command="{Binding FirstCommand}"&gt;&lt;/KeyBinding&gt;
      &lt;KeyBinding Key="F" Modifiers="Control" Command="{Binding SetFocusCommand}"&gt;&lt;/KeyBinding&gt;
  &lt;/UserControl.InputBindings&gt;
  &lt;TextBox Text="{Binding FilterText, UpdateSourceTrigger=PropertyChanged}"&gt;
      &lt;TextBox.InputBindings&gt;
          &lt;KeyBinding Gesture="Enter" Command="{Binding RelativeSource={RelativeSource AncestorType={x:Type UserControl }}, Path=DataContext.FilterCommand}"&gt;&lt;/KeyBinding&gt;
      &lt;/TextBox.InputBindings&gt;
  &lt;/TextBox&gt;
  </code></pre>
  
  <p>It seems function keys (<kbd>F1</kbd> etc) and <kbd>ALT</kbd>+<kbd>[key]</kbd> do work. I presume the <kbd>CTRL</kbd> and <kbd>SHIFT</kbd> modifiers are somehow 'blocking' the event from bubbling up to the UserControl.</p>