nHibernate query to outer join

Given this nhibernate query:

var cats = _nhibernateSession.QueryOver<SavedSearchResult>().Where(x => x.UserId == userId && x.IsDeleted == false).JoinQueryOver<SearchCategory>(x => x.Searc开发者_高级运维hCategory)
.List<SavedSearchResult>().ToList().GroupBy(c => c.SearchCategory.Id);

This works well but if a category does not have any search results, then we dont get the categories back.

Can anyone suggest an approach to this?

An outer join is expressed via QueryOver like this:

IQueryOver<Cat,Kitten> catQuery =
    session.QueryOver<Cat>()
        .Left.JoinQueryOver(c => c.Kittens)
            .Where(k => k.Name == "Tiddles");

(from the QueryOver docs on NHForge.org)

So, in your case, this will be:

var cats = 
      _nhibernateSession.QueryOver<Categories>()
                  .Left.JoinQueryOver(x => x.SearchCategory)
                  .Where (c => c.UserId == userId && c.IsDeleted = false );

I've omitted the group by clause, since I do not see any aggregated columns in your select. (Haven't tested the query as well though).