Convert Count ... Group By From SQL Query To LINQ

Question

Please help me convert the MSSQL below to LINQ.

SELECT A.id, A.type, COUNT(IIf(B.BookId IS NOT NULL, 0, null)) AS TotalCount
FROM Store A
LEFT JOIN Book B ON A.id = B.id
GROUP BY A.id, A.type;

I currently have this LINQ code:

from a in Store
join b in Book on a.id equals b.id into c
from d in c.DefaultIfEmpty()
group a by new
{
    a.id,
    a.type
} into g 
select new
{
    StoreId = g.Key.id,
    StoreType = g.Key.type,
    TotalCount = g.Key !=null?g.Count():0
}

I think I'm missing something important.

Answer 1

Since you're not trying to extract any values from the Book part of the join you don't need DefaultIfEmpty(), and since the join is a "group join" as a result of the into clause you don't need to group again:

from a in Store
join b in Book on a.id equals b.id into c
select new
{
    StoreId = a.id,
    StoreType = a.type,
    TotalCount = C.Count()
}