NHibernate JoinQueryOver

Question

Calling all NHibernate gurus out there!

If any one of you brainy folks could help me with the following conundrum I'd be most grateful:

I have some entities that describe RSS feeds from various sources that are grouped together in an entity called FeedList.

I am trying to select only the distinct SourceFeed entities that are linked with a given FeedList. (i.e "WHERE FeedList.name = 'feedlist1' ".

I've been playing around with JoinQueryOver for a while now but I just can't seem to work out how to get the required results.

The entities are related like this:

FeedList > Feed > FeedSource

So a FeedList contains many Feeds and each Feed belongs to a FeedSource.

Here is the code for the entities:

public class Feed
{
    public virtual int Id { get; set; }
    public virtual string Description { get; set; }
    public virtual FeedSource FeedSource { get; set; }
    public virtual string URL { get; set; }
}

public class FeedList
{
    public virtual int Id{get;set;}
    public virtual string Name { get; set; }
    public virtual IList<Feed> Feeds { get; set; }
}

public class FeedSource
{
    public virtual int Id { get; set; }
    public virtual string Name { get; set; }

}

I am using Fluent Automapping with the following overrides:

public class FeedOverride : IAutoMappingOverride<Feed>
{
    public void Override(AutoMapping<Feed> mapping)
    {
        mapping.References<FeedSource>(map => map.FeedSource).Cascade.All();   

    }
}

public class FeedListOverride : IAutoMappingOverride<FeedList>
{
    public void Override(AutoMapping<FeedList> mapping)
    {
        mapping.HasManyToMany<Feed> (map => map.Feeds).Cascade.All().Table("FeedList_Feed");

    }
}

Here is some code that creates some sample data:

 private static void CreateSampleData()
    {
        using (var session = HibernateHelper.OpenSession())
        {
            using (var transaction = session.BeginTransaction())
            {
                //Create source 1 and feeds

                FeedSource source1 = new FeedSource() { Name = "BBC" };

                IList<Feed> feedsForSource1 = new List<Feed>(){ 
                                                                    CreateFeed("Sample Feed1",source1,"http://feed1.xml"),
                                                                    CreateFeed("Sample Feed2",source1,"http://feed2.xml")
                                                                };

                FeedList feedList1 = CreateFeedList("FeedList1", feedsForSource1);




                //Create source 2 and feeds

                FeedSource source2 = new FeedSource() { Name = "Sky" };

                IList<Feed> feedsForSource2 = new List<Feed>(){ 
                                                                    CreateFeed("Sample Feed3",source2,"http://feed3.xml"),
                                                                    CreateFeed("Sample Feed4",source2,"http://feed4.xml"),
                                                                    CreateFeed("Sample Feed5",source2,"http://feed5.xml")
                                                                };

                FeedList feedList2 = CreateFeedList("FeedList2", feedsForSource2);

                session.SaveOrUpdate(feedList1);
                session.SaveOrUpdate(feedList2);


                transaction.Commit();
            }
        }
    }

What am I trying to achieve?

If I were to describe it (very poorly) in SQL, I'm looking to do something like this:

select  distinct *
from FeedList as list
LEFT JOIN FeedList_Feed as list_feed
ON list.Id = list_feed.FeedList_id
LEFT JOIN Feed as feed
ON feed.FeedSource_id = list_feed.Feed_id
LEFT JOIN FeedSource as src
ON src.Id = list_feed.Feed_id
WHERE list.Name="a feedlist name"

Thanks very much for your time :)

Answer 1

Ok so I've managed to work this out finally for anyone that's interested:

Entities

public class Feed
{
    public virtual int Id { get; set; }
    public virtual string Description { get; set; }
    public virtual FeedSource FeedSource { get; set; }
    public virtual string URL { get; set; }
    public virtual FeedList FeedList { get; set; }
}

public class FeedList
{
    public virtual int Id{get;set;}
    public virtual string Name { get; set; }
    public virtual IList<Feed> Feeds { get; set; }
}

public class FeedSource
{
    public virtual int Id { get; set; }
    public virtual string Name { get; set; }
}

Overrides

public class FeedOverride : IAutoMappingOverride<Feed>
{
    public void Override(AutoMapping<Feed> mapping)
    {
        mapping.References<FeedList>(map => map.FeedList).Cascade.All();
        mapping.References<FeedSource>(map => map.FeedSource).Cascade.All();
    }
}

public class FeedListOverride : IAutoMappingOverride<FeedList>
{
    public void Override(AutoMapping<FeedList> mapping)
    {
        mapping.HasManyToMany<Feed>(map => map.Feeds).Cascade.All().Table("FeedList_Feed");
        //mapping.HasMany<FeedListFeed>(map => map.Feeds).Cascade.All();
    }
}

And finally:

The Query

session.QueryOver<FeedList>()
                    .Inner.JoinAlias(f => f.Feeds, () => feedAlias)
                    .Where(fl => fl.Name == name)
                    .Select(x => feedAlias.FeedSource)
                    .List<FeedSource>().Distinct().ToList();