NHibernate aggregate query for one-to-many relation

Question

I have next entities:

class Topic
{
    public virtual int Id {get; private set;} 
    public virtual ICollection Votes {get; private set; }
}

class         


        

Answer 1

Provided you have a summary class to store your result :

public class  SummaryDTO
{
    public int TopicId { get; set; }
    public VoteType TypeOfVote { get; set; }
    public int VoteCount { get; set; }
}

then

Vote voteAlias = null;
SummaryDTO result = null;

youNHSession.QueryOver<Topic>()
  .JoinAlias(x=> x.Votes, ()=>voteAlias)
  .SelectList(
    list=>list
      .SelectGroup(topic=>topic.Id).WithAlias(()=>result.TopicId)            
      .SelectGroup(()=>voteAlias.VotedTo).WithAlias(()=>result.TypeOfVote)
      .SelectCount(()=>voteAlias.VotedTo).WithAlias(()=>result.VoteCount ))
  .TransformUsing(Transformers.AliasToBean<SummaryDTO>())
  .List<SummaryDTO>();

I guess that's not exactly what you are looking for, but hope this will set you on a good track.