如何在 LINQ 查询中获得带 GROUPBY 的 MAX 行？

我正在寻找一种方式在 LINQ 匹配下面的 SQL 查询。

Select max(uid) as uid, Serial_Number from Table Group BY Serial_Number

真的很需要帮助。由于 Group By语法，上面的查询获得每个序列号的最大 uid。

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最佳答案 
        using (DataContext dc = new DataContext())
{
var q = from t in dc.TableTests
group t by t.SerialNumber
into g
select new
{
SerialNumber = g.Key,
uid = (from t2 in g select t2.uid).Max()
};
}
小开 
var q = from s in db.Serials
group s by s.Serial_Number into g
select new {Serial_Number = g.Key, MaxUid = g.Max(s => s.uid) }
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I've checked DamienG's answer in LinqPad. Instead of 

g.Group.Max(s => s.uid)

should be

g.Max(s => s.uid)

Thank you!

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In methods chain form:

db.Serials.GroupBy(i => i.Serial_Number).Select(g => new
{
Serial_Number = g.Key,
uid = g.Max(row => row.uid)
});
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The answers are OK if you only require those two fields, but for a more complex object, maybe this approach could be useful:

from x in db.Serials
group x by x.Serial_Number into g
orderby g.Key
select g.OrderByDescending(z => z.uid)
.FirstOrDefault()

... this will avoid the "select new"

小开

This can be done using GroupBy and SelectMany in LINQ lamda expression

var groupByMax = list.GroupBy(x=>x.item1).SelectMany(y=>y.Where(z=>z.item2 == y.Max(i=>i.item2)));
小开

Building upon the above, I wanted to get the best result in each group into a list of the same type as the original list:

    var bests = from x in origRecords
group x by x.EventDescriptionGenderView into g
orderby g.Key
select g.OrderByDescending(z => z.AgeGrade)
.FirstOrDefault();


List<MasterRecordResultClaim> records = new
List<MasterRecordResultClaim>();
foreach (var bestresult in bests)
{
records.Add(bestresult);
}

EventDescriptionGenderView is a meld of several fields into a string. This picks the best AgeGrade for each event.


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