title: CollectionViewSource Items binding with value converter
body: <p>In my WPF application, there is a custom value converter where the Convert method receives a ReadOnlyObservableCollection value parameter.</p>
  
  <p>This value converter is called in XAML from the following binding:</p>
  
  <pre><code>&lt;TextBlock Grid.Column="2" Text="{Binding Items, Converter={StaticResource totalCutsConverter}}"/&gt;
  </code></pre>
  
  <p>Where Items comes from a CollectionViewSource with grouping descriptions difened as:</p>
  
  <pre><code>&lt;CollectionViewSource x:Key="sheetsViewSource" Source="{Binding}"&gt;
          &lt;CollectionViewSource.GroupDescriptions&gt;
              &lt;PropertyGroupDescription PropertyName="MaterialDescription" /&gt;
          &lt;/CollectionViewSource.GroupDescriptions&gt;
      &lt;/CollectionViewSource&gt;
  </code></pre>
  
  <p>Question is: How can I make my value converter receives a collection of my specific Items type (model class) instead of a generic object class?</p>
  
  <p>In other words, I would like to make the following cast in my Convert method</p>
  
  <pre><code>ReadOnlyObservableCollection&lt;myClass&gt; col = value as  ReadOnlyObservableCollection&lt;myClass&gt;();
  </code></pre>
  
  <p>Any ideas?</p>