Linq to NHibernate does not return proper data

Question

I have a class

public class Item : IItem
{
    public virtual Guid Id { get; set; }
    public virtual string Name { get; set; }
    public virtual bool IsActive { get; set; }
}
public interface IItem
{
    Guid Id { get; set; }
    string Name { get; set; }
    bool IsActive { get; set; }
}

public class ItemMap : ClassMap<Item>
{
    public ItemMap()
    {
        Id(x => x.Id);
        Map(x => x.Name);
        Map(x => x.IsActive);
    }
}

In my database I have created five items. Three that have the IsActive flag set to true and two that have it set to false.

When using the Interface it returns all five items:

        var q = from i in session.Linq<IItem>()
                where i.IsActive == true
                select i;

However, when using the concrete class it returns the proper three items:

        var q = from i in session.Linq<Item>()
                where i.IsActive == true
                select i;

EDIT
I have would like to return an Interface, because I have read that I should return non-concrete classes. Please note that in actuality, these Linq queries are in a repository in a different project (in case this becomes a web or WPF app)

Answer 1

I believe you will need to map IItem instead of the concrete Item class to have this work properly.

Answer 2

Things you could try:

• Instead of

  public class ItemMap : ClassMap<Item>
  

  use

  public class ItemMap : ClassMap<IItem>
  

• Simply cast the objects that are returned:

  var q = from i in session.Linq<Item>()
          where i.IsActive == true
          select (IItem)i;
  

Answer 3

It looks like a bug in the old contrib Linq provider.

Try with NHibernate 3, it works as expected.

Answer 4

I don't think you need to worry about querying against concrete types, that is fine. Just have your repository method return an interface. Make sense?

public IItem GetItem(int id)
{

  var item = from i in session.Linq<Item>()
                where i.IsActive == true
                select i;

  return item;

}

This will let you query work as it should and let all your dependent code work against the interface, which is all you really need the interface for anyway.