Question

I have a very simple grouping and aggregation problem in LINQ to SQL that I just can’t figure out, and it is driving me mad.

I’ve simplified things into this example:

class Customer {
public Guid Id;
public String Name;
}

class Order {
public Guid Customer_Id;
public double Amount;
}

How do I get a list of customers ordered by the number of orders they have? And on the total amount they have purchased for?

Answer 1

var qry1 = from c in db.Customers
           join o in db.Orders on c.Id equals o.Customer_Id into orders
           orderby orders.Count()
           select c;

var qry2 = from c in db.Customers
           join o in db.Orders on c.Id equals o.Customer_Id into orders
           orderby orders.Sum(o => o.Amount)
           select c;