Question

I have a set of objects that I’m returning via a Linq to SQL query. I’d like to modify the query so that I return a set of objects that are combined only when one of the fields match.

The relevant columns of my Products DB table are CategoryID and Quantity. I’d like to combine the fields so that if the CategoryID is identical, the Quantity fields are summed up. However, I don’t just want the sum – I need an object that has all the common fields (assume all other fields are identical for the query) so it appears as only one object of type Product.

Is this possible? (I’m using VB.net – but open to solutions that include database views, partial classes, etc)

Answer 1

It sounds like you want to Group on CategoryId and create a new Product based on aggregate data. E.g. (sorry if my VB is terrible):

From product In db.Products _
Group By CategoryID = product.CategoryID Into Group _
Select New Product With _
    CategoryID = CategoryID, _
    QuantityA = Group.Select(Function(p) p.QuantityA).Sum(), _
    QuantityB = Group.Select(Function(p) p.QuantityB).Sum()