title: Bind a property on data context to another object contained within the data context
body: <p>Consider the scenario shown below</p>
  
  <pre><code>class MyViewModel
  {
      public bool IsSelected {get;set;}
  }
  
  class SomeClass
  {
      public bool IsSelected {get;set;}
      public object Data {get;}
  }
  
  &lt;DataTemplate x:Key="ItemTemplate&gt;
      &lt;Image ... /&gt;
  &lt;/DataTemplate&gt;
  
  &lt;SomeControl ItemsSource={Binding MyViewModels}"
               ItemTemplate={StaticResource ItemTemplate}" /&gt;
  </code></pre>
  
  <p>The classes <code>SomeControl</code> and <code>SomeClass</code> are third party classes which I cannot modify. Internally, <code>SomeControl</code> creates instances of <code>SomeClass</code> and assigns my view model to its <code>Data</code> property. So, the data context of my ItemTemplate is <code>SomeClass</code></p>
  
  <p>I want to bind the <code>IsSelected</code> property on <code>SomeClass</code> to the <code>IsSelected</code> property of <code>MyViewModel</code>. How do I do that?</p>