title: joining on null to find missing elements
body: <p>I have a list of int called MyList; it comes as the result of a linq to sql query.
  I have a list of MyObject called ExistingObjectsList that contains an int as one of its properties.</p>
  
  <p>I'm looking to create a new list that contains all the ints that are in MyObjectsList but not in MyList.</p>
  
  <p>This is what I have so far:</p>
  
  <pre><code>var NewObjects = (from obj in MyObjectsList
                    join x in ExistingObjectsList on
                    obj.ID equals x into outer
                    from o in outer
                    where o == null
                    select o).ToList();
  </code></pre>
  
  <p>I'm sure it's simple but at the moment it's not working.</p>
  
  <p>Thanks for your suggestions.</p>