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);
}

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

Answer 1

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.

Answer 2

Almost five years later..., this is what you could do using NHibernate.Linq:

IList<string> names = session.Query<Tribble>().Select(t => t.Name).ToList()

Answer 3

What about executing a query by string?

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

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

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

Why would you want to do this?