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

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)
...