title: Escaping a WPF DataContext
body: <p>I'm very new to MVVM in particular.</p>
  
  <p>I have the following piece of XAML code:</p>
  
  <pre><code>&lt;ListBox x:Name="lsbTriggers" ItemsSource="{Binding SelectedProductPart.TriggerViewModels}"&gt;
              &lt;ListBox.ItemTemplate&gt;
                  &lt;HierarchicalDataTemplate &gt;
                      &lt;ComboBox SelectedItem="{Binding WatchedVariable}" 
                       ItemsSource="{Binding SelectedProductPart.AllVariables}" &gt;                            
                      &lt;/ComboBox&gt;
                  &lt;/HierarchicalDataTemplate&gt;
              &lt;/ListBox.ItemTemplate&gt;
          &lt;/ListBox&gt;
  </code></pre>
  
  <p>I'm trying to make a list that contains a combobox for each TriggerViewModel.</p>
  
  <p>The combobox's selected item is determined by the TriggerViewModel's WatchedVariable property.</p>
  
  <p>However, I want the ItemsSource of the combobox to be a list of variables provided by the SelectedProductPart object.
  I seem to be unable to do this because the datacontext has "zoomed in", if you will, on TriggerViewModels, due to it being the list's ItemsSource.</p>
  
  <p>I've tried creating a new DataContext inside the combobox, but this seems to create two disconnected DataContexts where changing the value of the combobox does not result in a change of TriggerViewModel's WatchedVariable.</p>
  
  <p>Is there a way I can escape the current DataContext so I can get to the SelectedProductPart's AllVariables list?</p>