Linq to SQL 按聚合排序

Question

我在 LINQ to SQL 中遇到一个非常简单的分组和聚合问题，但我无法弄清楚，这让我抓狂。

我将事情简化为这个例子：

class Customer { 公共引导 ID； 公共字符串名称； }

类订单 { 公共指导客户 ID； 公共双倍金额； ？

如何获取按订单数量排序的客户列表 他们购买的总金额是多少？

Answer 1

return dataContext.Customers.OrderBy(cust => cust.Orders.Count)
    .ThenBy(cust => cust.Orders.Sum(order => order.Amount))
    .ToList();

Answer 2

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;

Answer 3

按订单数量：

var customers = (from c in db.Customers
                 select new 
                  {
                    c.Name, 
                    OrderCount = c.Orders.Count()
                  }).OrderBy(x => x. OrderCount);

按购买总额：

var customers = (from c in db.Customers
                 select new 
                  {
                    c.Name, 
                    Amount = (from order in c.Orders
                              select order.Amount).Sum()
                  }).OrderBy(x => x.Amount);