title: Operation is not valid while ItemsSource is in use. Access and modify elements with ItemsControl.ItemsSource instead. Error while parsing XAML
body: <p>I get a runtime error that crashes when it tries to parse my <code>XAML</code>.</p>
  
  <pre><code>&lt;TreeViewItem Header="{Binding Header}" ItemsSource="{Binding DataGroups}"&gt;
      &lt;ListView ItemsSource="{Binding DataGroups}"&gt;
          &lt;ListView.View&gt;
              &lt;GridView&gt;
                  &lt;GridViewColumn Header="Group Name" DisplayMemberBinding="{Binding Path=Name}" /&gt;
                  &lt;GridViewColumn Header="Group Type" DisplayMemberBinding="{Binding Path=Type}" /&gt;
              &lt;/GridView&gt;
          &lt;/ListView.View&gt;
      &lt;/ListView&gt;
  &lt;/TreeViewItem&gt;
  </code></pre>