NHibernate: Getting single column from an entity

Question

How can you get a single column back from a query instead of a whole object?

I could do something like this to get the whole object, but all I want is the names:

IList<Tribble> tribbles = session.CreateCriteria(typeof(Tribble)).List<Tribble>();
IList<string> names = new List<string>();
foreach (Tribble t in tribbles) {
    names.Add(t.Name);
}

Update #1: I would like to be able to specify additional criteria, so is it possible to just exclude certain columns from being retrieved?

Update #2: See my answer below for the answer I discovered.

Answer 1

NHibernate is an OR mapper, and its purpose is to map database table data to objects. OR mappers are not generally designed to be general-purpose data query engines, thats ideally what databases are for. If you need to select a large set of single values, like a name, then your best option is to write a stored procedure that will return the required information.

When using ORM's, its always important to remember: Use the right tool for the job. Don't force a tool to serve a purpose it wasn't designed for.

Answer 2

You typically don't. It rarely makes sense to have a partially populated business object.

Why would you want to do this?

Answer 3

What about executing a query by string?

IList<string> names = session.CreateQuery("select name from Tribbles").List<strings>();

Answer 4

You can do something like this :

        IQuery query = dao.GetQuery("SELECT u.Id FROM UserImpl u WHERE u.UserName = :username");
  query.SetParameter("username", username);
  return (long)query.UniqueResult();

Answer 5

Here is the solution I eventually ended up using:

ICriteria c = session.CreateCriteria(typeof(Tribble));
c.SetProjection(Projections.ProjectionList().Add(Projections.Property("Name")));
IList<string> names = c.List<string>();

I got this idea from this old StackOverflow question.