title: Multiple ItemsSource collection bindings
body: <p>How can I binds multiple collections of different types to an ItemsSource of an ItemsControl?</p>
  
  <p>Using a single binding works fine:</p>
  
  <pre><code>&lt;ItemsControl ItemsSource="{Binding Foo}" /&gt;
  </code></pre>
  
  <p>But when I try a CompositeCollection, the items from <code>Foo</code> aren't displayed:</p>
  
  <pre><code>    &lt;ItemsControl&gt;
          &lt;ItemsControl.ItemsSource&gt;
              &lt;CompositeCollection&gt;
                  &lt;CollectionContainer Collection="{Binding Foo}" /&gt;
              &lt;/CompositeCollection&gt;
          &lt;/ItemsControl.ItemsSource&gt;
      &lt;/ItemsControl&gt;
  </code></pre>