Which O/R Mappers (.NET) support polymorphic queries?

I know NHibernate supports Polymorphic queries. The classic sample

from System.Object

will return all objects in the database.

Which other mappers support such types of queries?

LINQ2SQL definitely not. Genome (that's a good one too) also not. I'm not sure with Entity Framework.

This is a 100% must-have feature for a business application framework I'm currently planning. But I'm not so in favour for NHiber开发者_运维百科nate because I had bad performance experiences with large domain models (> 250 Entities) some years ago (1.1. Version)

Have you tried Telerik OpenAccess ORM. It's free for MS Sql Server.