title: Difference between two lists
body: <p>I Have two generic list filled with CustomsObjects.</p>
  
  <p>I need to retrieve the difference between those two lists(Items who are in the first without the items in the second one)  in a third one.</p>
  
  <p>I was thinking using <code>.Except()</code> was a good idea but I don't see how to use this..
  Help!</p>