LINQ to SQL中的SQL查询

Question

I am trying to write SQL query in LINQ to SQL but after 4h of trying i gave up.

select B.* from Bid B
join 
(
select BidId, max(BidVersion) as maxVersion
from Bid 
group by BidId
) X on B.BidId = X.BidId and B.BidVersion = X.maxVersion

i saw some tips on the stackOverflow but they werent helpful.

I am using some VERY bad code like:

        List<Bid> bidEntities = new List<Bid>();

        var newest = from bid in _dbContext.Bids
                    group bid by bid.BidId into groups
                    select new { Id = groups.Key, Vs = groups.Max(b => b.BidVersion) };

        foreach (var group in newest)
        {
            bidEntities.Add(await _dbContext.Bids.Where(b => b.BidId == group.Id && b.BidVersion == group.Vs).SingleOrDefaultAsync());
        }

Thank you for any advice.

Answer 1

Something like this should work:

var rows = Bids
            .GroupBy(b => b.BidId)
            .Select(g => g.OrderByDescending(gg => gg.BidVersion).FirstOrDefault())

With LINQ, it helps sometimes not to think in the 'SQL way', but about what you really want. You want the highest version bid for each BidId