How would one create this query using NHibernate QueryOver instead of Linq?

Question

I need to use QueryOver instead of Linq but am struggling to recreate the following query:

public IQueryable<AuctionItem> GetLiveAuctionItems(){
    repository.Query<AuctionItem>().Where(IsInActiveAuction()
}

 public static Expression<Func<AuctionItem, bool>> IsInActiveAuction()
        {
            var now = SystemTime.Now();
            var expression = PredicateBuilder.True<AuctionItem>();
            return expression.And
                (x => x.Lots.Any(
                    z => z.Auction.StartTime < now && z.Auction.EndTime > now && !z.DateWithdrawn.HasValue
                         && z.DateApproved.HasValue));
        }

I realise this creates subqueries but when I try to create using queryover I get errors stating projections needed.

Any help is much appreciated.

Answer 1

A quick draft with a clear how to steps. The first part, the subquery could look like this:

QueryOver<Lot> subQuery =
    QueryOver.Of<Lot>(() => lot)
    // Lot WHERE
    .WhereRestrictionOn(() => lot.DateWithdrawn).IsNull
    .AndRestrictionOn(() => lot.DateApproved).IsNotNull
    // Auction JOIN
    .JoinQueryOver<Auction>(l => l.Auction, () => auction)
        // Auction WHERE
        .Where(() => auction.StartTime < now)
        .Where(() => auction.EndTime > now)
    // AuctionItem.ID SELECT == projection
    .Select(Projections.Property(() => lot.AuctionItem.ID))
    ;

So, this will return the AuctionItem.ID, which does meet our seraching criteria. And we can use it like this:

AuctionItem auctionItem = null;
var query = session.QueryOver<AuctionItem>(() => auctionItem)
    .WithSubquery
    .WhereProperty(() => auctionItem.ID)
    .In(subQuery)
    ...