在LINQ中按和MIN（）分组

Question

Trying to convert the below SQL query to LINQ, but I'm stuck at grouping by ClientCompany.

SELECT TOP 300 ClientCompany,
CASE WHEN MIN(FeatureID) = 12 THEN 1 ELSE 0 END as Sort
FROM Ad
LEFT JOIN AdFeature
ON Ad.ID = AdFeature.AdID
WHERE (AdFeature.FeatureID = 13 OR AdFeature.FeatureID = 12)
AND SiteID = 2
GROUP BY ClientCompany
ORDER BY Sort DESC

My attempt to convert this to LINQ:

(from a in Ads
join af in AdFeatures
on new {
join1 = a.ID,
join3 = 2
} equals new {
join1 = af.AdID,
join3 = af.SiteID
}
let sort = (
af.FeatureID == 12 ? 1 : 0
)
orderby sort descending
where af.FeatureID == 13 || af.FeatureID == 12
select new { a.ClientCompany, sort } ).Take(300)

How would I use MIN(FeatureID) and GROUP BY ClientCompany in LINQ, so that I only get a single row per ClientCompany back?

EDIT

This worked! Based on Daniel Hilgarth's answer. Is there anything that can go horribly wrong with this solution?

Ads.Join(AdFeatures, x => x.ID, x => x.AdID,
(a, af) => new { Ad = a, AdFeature = af })
.Where(x => x.AdFeature.FeatureID == 12 || x.AdFeature.FeatureID == 13)
.Where(x => x.AdFeature.SiteID == 2)
.GroupBy(x => x.Ad.ClientCompany)
.Select(g => new { ClientCompany = g.Key, Sort = g.Min(x => x.AdFeature.FeatureID) == 12 ? 1 : 0 })
.OrderByDescending(x => x.Sort)
.Take(300)

Answer 1

Try this:

Ads.Join(AdFeatures, x => x.FeatureID, x => x.FeatureID,
         (a, af) => new { Ad = a, AdFeature = af })
   .Where(x => x.AdFeature.FeatureID == 12 || x.AdFeature.FeatureID == 13)
   .Where(x => x.AdFeature.SiteID == 2)
   .GroupBy(x => x.Ad.ClientCompany)
   .Select(g => new { ClientCompany = g.Key,
                      Sort = g.Min(x => x.AdFeature.FeatureID) == 12 ? 1 : 0 });

Please note, I changed the left outer join into an inner join, because your original query accesses AdFeature unconditionally, making it effectively an inner join .

Answer 2

Try this:

(from a in ads
 join af in AdFeatures on a.ID equals af.AdID into g
 from x in g.DefaultIfEmpty()
 where x.FeatureID == 13 || x.FeatureID == 12
 where x.SiteID == 2
 orderby a.Sort descending
 group a by a.ClientCompany into g2
 from x2 in g2
 let sort = g2.Select(T => T.FeatureID).Min() == 12 ? 1 : 0
 select new { a.ClientCompany, Sort = sort }).Take(300);

Why do you need grouping anyway?

Answer 3

hi I would write it like that

            context.Ads.Where(ad => ad.AdFeatures.Any(feature => (feature.FeatureID == 13 || feature.FeatureID == 12) && feature.SiteID == 2))
                   .GroupBy(ad => ad.ClientCompany)
                   .Select(ads => new
                   {
                       cc = ads.Key, sort = ads.SelectMany(ad => ad.AdFeatures)
                                               .Select(feature => feature.FeatureID)
                                               .Min() == 12
                   })
                   .OrderBy(arg => arg.sort).Take(300);