how can this SQL be done in LINQ? - linq

Question

i have this simple SQL query...
-- BestSeller
SELECT TOP(1) v.make, v.model, COUNT(v.make) AS NoSold
FROM Vehicles v
group by v.make, v.model
order by NoSold DESC
Im using entity framwork and want to do the same thing using linq. so far i have...
var tester = (from v in DB.VP_Historical_Vehicles
group v by v.make into g
orderby g.Count() descending
select new { make = g.Key, model = g, count = g.Count() }).Take(1);
foreach(var t in tester)
{
BestSeller.Make = t.make;
BestSeller.Model = t.make;
BestSeller.CountValue = t.count;
}
i keep getting timeouts, the database is large but the SQL runs very quick
any sugestions?
thanks
truegilly

Answer 1

Group by a compound key.
var t = (
from v in DB.VP_Historical_Vehicles
group v by new { v.make, v.model } into g
orderby g.Count() descending
select new { make = g.Key.make, model = g.Key.model, count = g.Count() }
)
.First();
BestSeller.Make = t.make;
BestSeller.Model = t.make;
BestSeller.CountValue = t.count;

Answer 2

Check what queries it performs when you run it with LINQ.
I suspect that you orderby g.Count() descending might be executing a COUNT query for each row and that would take a toll on performance to say the least.
When working with EF, always check what your LINQ statements produce in terms of queries. It is very easy to create queries that result in a n+1 scenario.

Answer 3

thanks to Scott Weinstein answer i was able to get it working
please comment if there is a more efficiant way of doing this...
VehicleStatsObject BestSeller = new VehicleStatsObject();
using (var DB = DataContext.Get_DataContext)
{
var t = (from v in DB.VP_Historical_Vehicles
group v by new { v.make, v.model } into g
orderby g.Count() ascending
select new { make = g.Key.make, model = g.Key.model, count = g.Count() }).OrderByDescending(x => x.count).First();
BestSeller.Make = t.make;
BestSeller.Model = t.model;
BestSeller.CountValue = t.count;
}
return BestSeller;