How can I return multiple results from a single LinQ to SQL expression in one round-trip?

I'm rewriting an ancient piece of code that I've inherited and I'm looking at a query that performs a massive join on large tables, and then does a series of grouping actions on the resulting table to "distill out" data:

INSERT INTO #teh_temp_table
SELECT * FROM teh_large_table
INNER JOIN teh_other_large_table

SELECT customer_id, customer_name FROM * #teh_temp_table
GROUP BY customer_id, customer_name
ORDER BY customer_name

SELECT city_id, city_name FROM * #teh_temp_table
GROUP BY city_id, city_name
ORDER BY city_name

-- repeated n-2 times ...

This large SQL statement is sent to the DB server with a ADO.NET SqlCommand, and the data is returned as n separate results in one network round trip.

I'm having difficulties translating this to LinQ to SQL. I've been attempting to do something similar to:

开发者_如何转开发from tlt in teh_large_table
join tolt in teh_other_large_table on tlt.pkey equals tolt.fkey into teh_temp_table

from tmp in teh_temp_Table
group tmp by new { tmp.customer_id, tmp.customer_name } into customers

from tmp in teh_temp_table 
group tmp by new { tmp.city_id, tmp.city_name } into cities

select new { customers, cities }

but the compiler complains. Is there a way to issue an equivalent LinQ query that not only retrieves the data but also returns it, in a single network round-trip? As you can imagine, I don't want to perform that big nasty join more than once.

---

Other than trying to force distinct on the result sets, I'm not seeing the advantage of using the Group operation here. Since LINQ to SQL can't return multiple results from LINQ, you could push them into a your temp table and then group the results based on some type. Would the following work for you:

var bigTable = from large in teh_large_table
               from other in teh_other_large_table
               select new { ??? }; // TODO: Supply needed columns here

var kvPairs = from customer in bigTable
              select new {Id = customer.Customer_id, Name = customer.Customer_name, Type="Customer"}
              .Union(
              from city in teh_temp_table
              select new {Id = city.City_id, Name = city.City_name, Type="City"}
              ).Distinct();

var groupedKvPairs = from pair in kvPairs
                     group pair by pair.Type into grouped
                     select new {pairType = key, 
                                 vals = from row in grouped
                                        orderby row.Name
                                        select new { row.Id, row.Name}};

As an alternative, you could also set up a Stored Proc returning multiple results and then use the IMultipleResults interface to consume them. See http://www.thinqlinq.com/Default/Using-LINQ-to-SQL-to-return-Multiple-Results.aspx