NHibernate Queryover - How do I return only a child collection

Question

I am running into difficulty with the following nhibernate queryover query. I am probably over-complicating things, but here is the problem:

• I have an entity named AuctionStatistic that links to an auction (this is uni-directional and I do not have links from auctions back to statistics)
• I would like to query the statistic table, find all auction IDs and pull back only those that meet a certain threshold - i.e. top 500 auctions by views
• Once I've gotten the top X (in this example i'm hardcoding to 10000 views) I want to pull back the auction id and name. For this particular query I don't need any of the data stored in the statistics table (though this is used elsewhere and is not redundant)

I figured I could use something like the following to get back just the auctions, but because I'm querying over AuctionStatistic it expects the selected value to be of type AuctionStatistic (or a list thereof)

var auctions = _session.QueryOver<AuctionStatistic>().Where(c => c.ViewCount > 10000).Fetch(x=>x.Auction).Eager.Select(x=>x.Auction);

Can anyone suggest a better way of doing this?

Thanks

JP

Answer 1

Without bi-directional this is probably your best bet.

Auction auctionAlias = null;
AuctionDTO dto = null;

var auctionDtos = _session.QueryOver<AuctionStatistic>()
    .Where(c => c.ViewCount > 10000)
    .JoinAlias(x => x.Auction, () => auctionAlias)
    .SelectList(list => list
        .Select(() => auctionAlias.id).WithAlias(() => dto.id)
        .Select(() => auctionAlias.name).WithAlias(() => dto.name))
    .TransformUsing(Transformers.AliasToBean<AuctionDTO>())
    .List<AuctionDTO>();