Question

Have the following (non-straightforward) T-SQL query, which i’m trying to convert to LINQ (to be used in a L2SQL expression):

declare @IdAddress int = 481887

select * from 
(
    select top 3 p.* 
    from tblProCon p
    inner join vwAddressExpanded a
    on p.IdPrimaryCity = a.IdPrimaryCity
    where a.AddressType = 3
    and p.IsPro = 1
    and a.IdAddress = @IdAddress
    order by AgreeCount desc
) as Pros

union

select * from 
(
    select top 3 p.* 
    from tblProCon p
    inner join vwAddressExpanded a
    on p.IdPrimaryCity = a.IdPrimaryCity
    where a.AddressType = 3
    and p.IsPro = 0
    and a.IdAddress = @IdAddress
    order by AgreeCount desc
) as Cons

order by ispro desc, AgreeCount desc

In a nutshell, i have an @IdAddress – and i’m trying to find the top 3 pro’s and top 3 con’s for that address.

The above query does work as expected. I’m not entirely sure how to convert it to a LINQ query (never done unions before with LINQ). I don’t even know where to start. 🙂

Query-style/Lambda accepted (prefer query-style, for readability).

Also – i have LinqPad installed – but i’m not sure how to “convert T-SQL to Linq” – is there an option for that? Bonus upvote will be awarded for that. 🙂

The above T-SQL query performs well, and this L2SQL query will be executed frequently, so it needs to perform pretty well.

Appreciate the help.

Answer 1

var baseQuery = (from p in db.tblProCon
                join a in db.vwAddresssExpanded
                on p.IdPrimaryCity equals a.IdPrimaryCity
                where a.AddressType == (byte) AddressType.PrimaryCity &&
          a.IdAddress == idAddress
          order by p.AgreeCount descending
                select p);

var pros = baseQuery.Where(x=> x.IsPro).Take(3);
var cons = baseQuery.Where(x=> !x.IsPro).Take(3);

var results = pros
               .Union(cons)
               .OrderByDescending(x => x.IsPro)
               .ThenByDescending(x => x.AgreeCount)
               .ToList();