title: linq union of two lists
body: <p>I have an object model that contains a list of longs. I want to get the combined list of longs of two different instances. When I write this:</p>
  
  <pre><code>var MyCombinedList = TheObject1.ListOfLongs.Union(TheObject2.ListOfLongs);
  </code></pre>
  
  <p>I get an empty list. Note that sometimes <code>TheObject2</code> can have an empty list.</p>
  
  <p>What am I doing wrong?</p>
  
  <p>Thanks.</p>