Selecting a joined entity with an ICriteria in NHibernate

Question

Hi, In HQL I can do something like this:

select roleHeldByOwner.TargetPerson from Person roleOwner join roleOwner.RolesOnPeople roleHeldByOwner where roleOwner.Id = :roleOwnerId

How can I achieve the same thing in a Criteria query? Specifically the selecting of something that isn't the first entity in the From clause.

Thanks, Matt

Answer 1

You can join by creating sub-criteria and select scalar results with Projections. Your Criteria query might look something like:

session.CreateCriteria(typeof(Person))
    .Add(Restrictions.Eq("Id", roleOwnerId))
    .SetProjection(Projections.Property("TargetPerson"))
    .CreateCriteria("RolesOnPeople", JoinType.InnerJoin) // Or LeftOuterJoin, etc.
    .List();

If you need multiple projections, use a ProjectionList like:

.SetProjection(Projections.ProjectionList()
    .Add(Projections.Property("...", ...))
    .Add(...)
    ...
)

I'm not sure what your domain looks like or what you're trying to get out of the query so the above may not be exactly correct. However, it should be what you need to get started.