T-Sql to linq conversion issues (order by) - asp.net

Question

I'm having a bit of issue converting the following t-sql statement to Linq (using 4.0 entity framework)
I'm getting
Unable to cast the type
'System.Linq.IOrderedQueryable1' to
type 'System.Linq.IQueryable1'. LINQ
to Entities only supports casting
Entity Data Model primitive types.
T-Sql
SELECT
I.Id
, I.Name
FROM Inventory I
WHERE I.Id in
(
select top 5 applicationId
from LastViewed
group by ApplicationId, SomeUserId
having SomeUserId = #SomeUserId
order by Max(id) desc
)
This is what I have right now (with help from Linqer)
Dim query As IQueryable(Of Inventory) =
From d In ctx.Inventories
Where
((From e In ctx.LastVieweds _
Group e By _
e.ApplicationId, _
e.SomeUserId _
Into g = Group _
Where DfaitEdsId = user _
Order By g.Max(Function(p) p.Id) Descending _
Select New With { _
ApplicationId _
}).Take(5)).Contains(New With {.ApplicationId = d.Id}) _
Select d
it currently crashes when I do this line.
query.ToList()
Thanks for your time.

Answer 1

Your 'problem' is in your very first line. The query you have specified returns an IOrderedQueryable(Of Inventory) that you are trying to assign to a variable of type IQueryable(Of Inventory). You aren't getting the error until query.ToList() thanks to deferred execution. You can let the compiler infer the type if you have 'option infer' set to on in your project and your query would be something like:
Dim query =
From d In ctx.Inventories
Where
(From e In ctx.LastVieweds _
Group e By _
e.ApplicationId, _
e.SomeUserId _
Into g = Group _
Where DfaitEdsId = user _
Order By g.Max(Function(p) p.Id) Descending _
Select ApplicationId Take 5 _
).Contains(d.Id) _
Select d
Or you can just change the type of query to be IOrderedQueryable(Of Inventory)
Note: What you have works fine in Linq to SQL, but Entities is much stricter when it comes to casting.
Edit:
Alright, let's try to dig a little deeper into this. Tell me which line blows up with the following:
Dim innerList = (From e In ctx.LastVieweds _
Group e By _
e.ApplicationId, _
e.SomeUserId _
Into g = Group _
Where DfaitEdsId = user _
Order By g.Max(Function(p) p.Id) Descending _
Select ApplicationId Take 5).ToList()
Dim query = (From d In ctx.Inventories
Where innerList.Contains(d.Id) _
Select d).ToList()
Don't forget to pare the results down a bit if enumerating the queries with 'ToList()' is too much. The types of both variables are now List(Of Inventory)