title: Except() on EntityCollection vs List
body: <p>Using EntityFramework 4. I have an <code>EntityCollection&lt;SomeEntity&gt; currentEntities</code> with ~500k entities and a <code>List&lt;SomeEntity&gt; importedEntities</code> also with ~500k records. I want to have the list of all records occuring in <code>currentEntities</code> which don't exist in <code>importedEntities</code>.</p>
  
  <p>Calling <code>currentEntities.Select(x =&gt; x.ID).Except(importedEntities.Select(x =&gt; x.ID))</code> to get unique IDs of occurring records causes a <code>System.OutOfMemoryException</code> because it apparently loads all of the entities into the memory.</p>
  
  <p>Calling <code>currentEntities.Where(x =&gt; !importedEntities.Any(y =&gt; y.ID == x.ID))</code> fails with <code>NotSupportedException</code> ("Only primitive types ('such as Int32, String, and Guid') are supported in this context").</p>
  
  <p><code>currentEntities</code> is on the SQL Server 2008 R2 database, while <code>importedEntities</code> are in memory.</p>
  
  <p>Is this even possible in L2E ?</p>