Sorting linked collection in Nhibernate query

Question

This is partly related to this.
I'd like to find a way to sort of a linked (HasMany) collection result directly in the Nhibernate query.

 ICriteria criteria = Session.CreateCriteria(typeof(PortalPage));
 criteria.CreateAlias("PartialViews", "vc");
 criteria.AddOrder(Order.Asc("vc.ColumnNumber"));
 criteria.Add(Property.ForName("Url").Eq(pageUrl));
 return criteria.UniqueResult<PortalPage>();

Correcly generates a select with the ORDER BY but the result in the linked collection is not ordered.

I'd like to avoid sorting the collection after the result is returned (like using linq to objects) is this possible?

UPDATE: As Steve suggested the problem can be solved by hard coding the order attribute in the mapping like:

HasMany(x => x.PartialViews).KeyColumnNames.Add("PageId").AsBag().SetAttribute("order-by", "ColumnNumber");

Answer 1

Have you specified the collection as a list type rather than a bag or a set? If you make sure to use a list mapping type and specify an index column for the list mapping everything should be taken care of for you.

See the docs here, and there's some more info here too, although that second one is an older post so watch out for things that may have changed.

Here's a simple list collection mapping example:

<list name="Images table="Images">
  <key column="Id"/>
  <index column="Position"/>
  <element type="String" column="FileName"/>
</list>

The fluent mapping for this example would be something like this:

HasMany(x => x.Images).AsList(x => x.WithColumn("Position"));