Linq to SQL order by aggregate

Question

我在LINQ to SQL中有一个非常简单的分组和聚合问题，我就是搞不明白，这让我抓狂。

我已将其简化为以下示例：

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

类订单{公共Guid Customer_Id；公共双倍金额；}

如何获取按订单数排序的客户列表？他们购买的总金额是多少？

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;

Answer 2

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

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);

按购买总额计算：

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);