title: CollectionViewSource Violates MVVM
body: <p>I have an MVVM app and in a couple of my VMs I use <code>CollectionViewSource.GetDefaultView(datasource)</code> to initialize my ICollectionView and it works perfectly. 
  My concern is that am I violating MVVM when using the CVS in my VMs?</p>
  
  <p>Thank you all for your inputs</p>