title: EF4 (CPT5) ForeignKeyAttribute in base class - Assert Failure entityType != null
body: <p>Getting an error when trying to set a ForeignKeyAttribute in a base class</p>
  
  <pre><code>class User { }
  
  abstract class FruitBase
  {    
     [ForeignKey("CreateById")]
     public User CreateBy{ get; set; }
  
     public int CreateById{ get; set; }     
  }
  
  class Banana : FruitBase { }
  
  class DataContext : DbContext
  {    
     public DbSet&lt;Banana&gt; Bananas { get; set; }
  }
  </code></pre>
  
  <p>If I move the FruitBase code into the banana, all is well, but I don't want to, as there will be many many fruit and I want to remain relatively DRY if I can</p>
  
  <p>Is this a know issue that will be fixed by March?
  Does anyone know a work around?</p>