Fluent NHibernate - Query over a derived class

Lets say I have two classes:

public class A
{
  public virtual int Id { ge开发者_StackOverflowt; set; }
  public virtual Object1 Obj { get; set; }
}

public class B : A
{
  public new virtual Object2 Obj { get; set; }
}

I use Fluent NHibernate and I have created two different mappings for the two classes. However, when I try to query class A in my repository, FNH finds both class B and A, which kind of makes sense since both are A.

Example (this criteria will query over both A and B):

public List<T> GetByName(string name)
{
  return Session.CreateCriteriaOf<A>.Add(Restrictions...);
}

When writing CreateCriteriaOf<A>, I only want to query over A - not B. How can I solve my problem?

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I think you better make an inheritance tree where both A and B derive from a common (abstract) base type. Then NHibernate can make the distinction by a discriminator column.

Of course, your data model should accommodate this, so I hope your model is not prescribed in any way.