I recently switched to LLBLGen 2 and it looks like the following code's behavior changed. Now it populates childEntity.Parent.ChildCollection with duplicated ChildEntity 12345.

ChildEntity childEntity = new ChildEntity(12345);
IPrefetchPath2 prefetchPath = new PrefetchPath2((int)EntityType.ChildEntity);
prefetchPath.Add(ChildEntity.PrefetchPathParent).SubPath.Add(ParentEntity.PrefetchPathChildCollection);
using (DataAccessAdapter adapter = new DataAccessAdapter())
{
     adapter.FetchEntity(childEntity, prefetchPath);
}

Is this change intentional?

See: http://www.llblgen.com/tinyforum/Messages.aspx?ThreadID=6852

Found a workaround:

ChildEntity childEntity = new ChildEntity(12345);
IPrefetchPath2 prefetchPath = new PrefetchPath2((int)EntityType.ChildEntity);
prefetchPath.Add(ChildEntity.PrefetchPathParent).SubPath.Add(
          ParentEntity.PrefetchPathChildCollection, 
          0, 
          new PredicateExpression(ChildFields.Id != 12345));
using (DataAccessAdapter adapter = new DataAccessAdapter())
{
     adapter.FetchEntity(childEntity, prefetchPath);
}