Fairly complex LINQ to Entities query - entity-framework

Question

I have two entities, assume they are called Container and Record. They have a master-child relationship: a 'container' can hold many records.
The Records table in the database has the following columns:
Id
Date
Container_Id
RecordType_Id
The Record entity does not have any navigation properties that back reference the Container.
I am writing a LINQ query for my repository that will retrieve ONLY the records for a container that have the most recent date for each RecordType_Id. All older records should be ignored.
So if a container has say 5 records, one for each RecordType_Id, with the date 24/May/2011. But also has another 5 records for each RecordType_Id but with the date 20/May/2011. Then only the first 5 with the 24/May date will be retrieved and added to the collection in the container.
I came up with an SQL query that does what I need (but maybe there is some more efficient way?):
select t.*
from Records t
inner join (
select Container_Id, RecordType_Id, max(Date) AS MaxDate
from Records
group by Container_Id, RecordType_Id ) g
on t.Date = g.MaxDate
and t.Container_Id = g.Container_Id
and t.RecordType_Id = g.RecordType_Id
order by t.Container_Id
, t.RecordType_Id
, t.Date
However I am struggling to translate this into a proper LINQ query. EF is already generating a fairly large query all by itself just to load the entities, which makes me unsure of how much of this SQL query is actually relevant to the LINQ query.

Answer 1

Off the top of my head:
var q = from c in Container
from r in c.Records
group r by r.RecordType.RecordType_Id into g
select new
{
Container = c,
RecordType_Id = g.Key,
Records = from gr in g
let maxDate = g.Max(d => d.Date)
where gr.Date == maxDate
select gr
};

Answer 2

Try using LinqPad, it helps you test linq queries easily. Even against an existing EF model (which is in your project). Visit http://www.linqpad.net/