title: DbContext's ChangeTracker problem
body: <p>I have a codefirst EF-4.1 based program. The user gets a context and can modify some properties. When the user is done, I do a quick</p>
  
  <pre><code>ChangeTracker.Entries().Any(e =&gt; e.State != EntityState.Unchanged);
  </code></pre>
  
  <p>to determine if a <code>SaveChanges()</code> is required or not. If I do a 'SaveChanges()' call, the changes that have made are persisted to the database.</p>
  
  <p>This works for some properties, and doesn't work for others. Specifically it seems to work with simple types (<code>float</code>s), and with collection hierarchies(<code>ObservableCollection</code>s). </p>
  
  <p>Am I doing something wrong?</p>