title: Access MVVM parent view model from within collection
body: <p><img src="https://i.stack.imgur.com/E2IT6.png" alt="alt text"></p>
  
  <p>The picture above illustrates my program. Arrows indicate <code>Binding</code>.</p>
  
  <p>My MainWindow.xaml has its datacontext set as <code>MainVM</code>.</p>
  
  <p>The Window has a tab control binded to a <code>ObservableCollection</code> of <code>ViewModel</code>s. Using a data template, the tab control displays views corresponding to the <code>ViewModel</code>. </p>
  
  <p>The <code>ObservableCollection</code> is found in <code>MainVM</code>.</p>
  
  <p>How do I access properties found in <code>MainVM</code> from <code>ViewModel</code> (enclosed in the ObservableCollection)?</p>
  
  <p>I am open to answers that are require modification of my programming model.</p>