LINQ with multiple columns and operations

Question

i'm trying to do this on LINQ:

select p.ProductID, p.ArticleCode, SUM((case h.OperationType when 0 then 1 else -1 end) * h.[Count])
from Products p
inner join StockItems s on p.ArticleCode = s.ArticleCode
inner join StockHistorical h on s.ArticleID = h.ArticleID
where h.[Date] < '23/08/2013 11:30:00'
group by p.ProductID, p.ArticleCode

I have this:

        var products = (from p in e.Products
                        join s in e.StockItems on p.ArticleCode equals s.ArticleCode
                        join h in e.StockHistoricals on s.ArticleID equals h.ArticleID
                        where h.Date < DateTime.Parse("23/08/2013 11:30:00")
                        group p by p.ProductID into StockResult
                        select new {  });

Anyone know how can i do the

SUM((case h.OperationType when 0 then 1 else -1 end) * h.[Count])

with LINQ?

Thanks!

I forgot to say that the problem is the "group by", because i can't access the OperationType property in the StockResult group.

Solved! The key is the:

let combined = new 
{
    Product = p,
    HistoryCount = (h.OperationType == 0 ? 1 : -1) * h.Count
}

Answer 1

...
let combined = new 
{
    Product = p,
    HistoryCount = (h.OperationType == 0 ? 1 : -1) * h.Count
}
group combined by combined.Product.ProductID into StockResult
select new
{
    ProductID = StockResult.Key,
    Total = StockResult.Sum(x => x.HistoryCount)
}

Answer 2

It's not a direct translation, but I'd go with:

(h.Count(his => his.OperationType != 0) 
    - h.Count(his => his.OperationType == 0))
    * h.Count()

It should be functionally equivalent, and seems to better represent what you're trying to do.

Answer 3

You are trying to do something like this? I am not sure this is going to work.

select new
{
S=Sum(((h.OperationType)!=0?-1:1)*h.Count)
}