linq - How to get top 10 customers based on values of orders -

i have list of customers each have list of orders. each order has list of lineitems.

i write linq query me top 10 customers based on order value (i.e. money spent) , not total number of orders.

one customer have 2 orders have spent £10,000, customer have 100 orders, , spent £500.

right now, have gets me top 10 customers number of orders.

var customers = (from c in _context.customers c.saleorders.count > 0         let activecount = c.saleorders.count(so => so.status != saleorderstatus.cancelled)         orderby activecount descending         select c).take(10); 

update

thanks jon skeet's comment doing double sum, wrote following query compiles.

var customers = (from c in _context.customers c.saleorders.count > 0         let ordersum = c.saleorders.where(so => so.status != saleorderstatus.cancelled).sum(so => so.lineitems.sum(li => li.calculatetotal()))         orderby ordersum descending         select c).take(10); 

but when run this, following error:

it seems linq doesn't recognise .calculatetotal() method sit on lineitem.cs entity.