How do I get the MAX row with a GROUP BY in LINQ query?
.NetLinqLinq to-Sql.Net Problem Overview
I am looking for a way in LINQ to match the follow SQL Query.
Select max(uid) as uid, Serial_Number from Table Group BY Serial_Number
Really looking for some help on this one. The above query gets the max uid of each Serial Number because of the Group By
Syntax.
.Net Solutions
Solution 1 - .Net
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()
};
}
Solution 2 - .Net
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) }
Solution 3 - .Net
In methods chain form:
db.Serials.GroupBy(i => i.Serial_Number).Select(g => new
{
Serial_Number = g.Key,
uid = g.Max(row => row.uid)
});
Solution 4 - .Net
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!
Solution 5 - .Net
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"
Solution 6 - .Net
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)));