Sum and Count in EF

It bugs me that I need to play around with casting in linq expressions just to make aggregate functions safe. For example:

decimal? total = storeDb.Carts
                   .Where(cart => cart.CartId == ShoppingCartId)
                   .Select(c => (decimal ?)c.Count * c.Album.Price)
                   .Sum();

See that (decimal ?) cast?

If you haven’t encountered it before, it’s because of what will happen if the result of the query is a null list:

The cast to value type ‘Decimal’ failed because the materialized value is null

It only happens when linq to sql gets involved, a linq object query against objects in an array (say) would be fine…

And no, neither of the fields in the database are nullable