title: Strange focus behavior for simple WPF ItemsControl
body: <p>I'm seeing strange behavior when it comes to focus and keyboard navigation. In the example below I have a simple ItemsControl that has been templated so that it presents a list of CheckBoxes bound to the ItemsSource.</p>
  
  <pre><code>&lt;ItemsControl FocusManager.IsFocusScope="True"
                ItemsSource="{Binding ElementName=TheWindow, Path=ListOStrings}"&gt;
      &lt;ItemsControl.ItemTemplate&gt;
          &lt;DataTemplate&gt;
              &lt;CheckBox Content="{Binding}" /&gt;
          &lt;/DataTemplate&gt;
      &lt;/ItemsControl.ItemTemplate&gt;
  &lt;/ItemsControl&gt;
  </code></pre>
  
  <p>For some strange reason the <em>FocusManager.IsFocusScope="True"</em> assignment causes keyboard focus to fail to be set when checking a checkbox via a mouse click and for focus to jump out of the ItemsControl when a check box is checked using the space bar on the keyboard. Both symptoms seem to point to some strange navigation happening when the checkbox is checked but I'm having a hard time getting to the bottom of it.</p>
  
  <p>This problem occurs if I set any parent element up the visual tree as a focus scope using this method. If I remove the <em>FocusManager.IsFocusScope="True"</em> then the problems go away. Unfortunately I'm seeing this problem in a larger project where I cannot just remove these focus scopes without worrying about other focus related consequences.</p>
  
  <p>Could somebody explain to me the strange behavior I'm seeing? Is this a bug or am I just completely missing something?</p>