NHibernate query collection - nhibernate

Question

I have a users and roles table. A user can have multiple roles.
I want to grab all of the users without a specific role. The problem is if a user has 2 roles, one being the role we don't want, the user will still be returned.
public IList<User> GetUserByWithoutRole(string role)
{
return CreateQuery((ISession session) => session.CreateCriteria<User>()
.CreateAlias("Roles", "Roles")
.Add(!Restrictions.Eq("Roles.RoleDescription", role))
.List<User>());
}
The only solution I came up with was client side
public IEnumerable<User> GetUserByWithoutRole(string role)
{
return CreateQuery((ISession session) => session.CreateCriteria<User>()
.CreateAlias("Roles", "Roles")
.Add(!Restrictions.Eq("Roles.RoleDescription", role))
.List<User>()).Where(u => u.Roles.FirstOrDefault(r => r.RoleDescription == role) == null);
}
Anyone know of a better solution? Thanks!

Answer 1

Alternatively you can use Criteria API to create subquery
var subquery = DetachedCriteria.For<Role>("role");
subquery.Add(Restrictions.EqProperty("role.User.id", "user.id"))
.SetProjection(Projections.Property("role.RoleDescription"));
var users = session.CreateCriteria<User>("user")
.Add(Subqueries.NotIn(role, subquery))
.List<User>();

Answer 2

If you want to do that in nhibernate you'll have to do two queries or a subquery. Here is a similar post:
FluentNHibernate query on many-to-many relationship objects

Answer 3

Thanks, for anyone interested this is what I finished up with:
public IEnumerable<User> GetUserByWithoutRole(string role)
{
var subQuery = DetachedCriteria.For<User>()
.CreateAlias("Roles", "Roles")
.SetProjection(Projections.Property("UserID"))
.Add(Restrictions.Eq("Roles.RoleDescription", role));
return _session.CreateCriteria<User>()
.SetResultTransformer(new DistinctRootEntityResultTransformer())
.Add(Subqueries.PropertyNotIn("UserID", subQuery))
.AddOrder(Order.Asc("FirstName"))
.List<User>();
}