title: Comparing two lists to get objects that appear in both
body: <p>I have two lists of the same class, and want to generate a count of objects that appear in both lists.</p>
  
  <pre><code>Dim repeatingMentions As Integer 
  repeatingMentions =currentMentions.Where(Function(m) previousMentions.Contains(m)).Count
  </code></pre>
  
  <p>Debugging I can see that the two lists contain objects with exactly the same property values, is this enough to satisfy contains because the count is coming back as 0.</p>