NHibernate projection help - nhibernate

Question

Im having a problem creating a projection for my nhibernate detachedcriteria object.
I have a class Spa which is linked to table Address.
Address has a field called City which is a string.
public class Spa : IAggregateRoot
{
[BelongsTo("AddressID", Cascade = CascadeEnum.All)]
public Address Address { get; set; }
}
My ultimate goal is to get a distinct list of City names.
If i could get all spas with distinct cities i would be happy too.
All my attempts have been for naught and havent found any helpful posts.
So far i've tried:
DetachedCriteria query = DetachedCriteria.For<Spa>()
.CreateAlias("Address", "A")
query.SetProjection(
Projections.Distinct(Projections.ProjectionList()
.Add(Projections.Alias(Projections.Property("Address"), "A"))));
var Spas = ActiveRecordMediator<Spa>.FindAll(query);
I know the above is not correct, just trying to find somewhere to start.
Any help would be appreciated.
Also any simple projections tutorials would be appreciated, cant seem to find anything straight forward out there.
I also tried, but got cast error, looking into it:
DetachedCriteria query = DetachedCriteria.For<Spa>()
.CreateAlias("Address", "A")
.SetProjection(Projections.Distinct(Projections.Property("A.City")));

Answer 1

It seems to me there are two parts to your question.
1. What should my DetachedCriteria look like?
If you are not performing any other aggregations, GROUP BY should provide the same results as DISTINCT. This is the query I would use:
var query = DetachedCriteria.For<Spa>()
.CreateAlias("Address", "A")
.SetProjection(Projections.GroupProperty("A.City"));
2. How do I execute it with Castle ActiveRecord?
I have never used ActiveRecord, but based on the method signatures, I would expect something like this to work:
var cities = ActiveRecordMediator<string>.FindAll(query);
If you have access to the NHibernate session, you could also execute it this way:
var cities = query.GetExecutableCriteria(session).List<string>();