Sum nested values with Linq

Question

Simple problem: I have Users that can have many Orders that can have many Products. What does the Linq (lambda) query look like to get a User\'s grand total of all Product.Pric

Answer 1

int total = (from user in users
             from order in user.Orders
             from product in order.Products
             select (int?)product.Price).Sum() ?? 0;

would be my offering; there is an annoying glitch that the SUM in SQL over 0 rows is NULL, not 0 - the above works around that.

or as lambdas (from comments):

int total = users.SelectMany(user => user.Orders)
                 .SelectMany(order => order.Products)
                 .Sum(product => (int?)product.Price) ?? 0;