无法通过NHibernate LINQ进行分组

Question

I'm having hard times to perform simple grouping on my entities. The faulting line of code is

var xxx = jobQuery.GroupBy(j => j.EverifyCase)
    .Select(g => new { EC = g.Key, MRJ = g.Last() })
    .ToList();

This gives me the following HibernateException:

Query Source could not be identified: ItemName = < generated >_1, ItemType = EverifyCaseJob, Expression = from EverifyCaseJob _1 in [ec]

If I do jobQuery.ToList() everything is peachy - so I guess the problem is with the GroupBy() The "Query Source" could be identified as I use this entity all over the place, but not in conjunction with GroupBy() so far.

Any ideas?

Also, could anyone explain what the error message means?

NHibernate version is 4.0.3.4000

I also use Fluent NH - version 2.0.1.0

Answer 1

Sql is set based and has no order in a grouping group. So it has no meaning of last in a group hence NHibernate can not translate it to sql. Max on the other side is well defined for a set and will work fine.