linq - 如何在 LINQ 中对多个表进行分组

Question

所以，我理解 group by 的工作原理基本上是这样的:

var query = from c in context.Contacts
            join o in context.Orders on c.Id on o.CustomerId
            group c by o.Id
            select new { g.Key, g.Sum(c => c.Whatever) };

这样的分组只允许我访问 c 的内容。但是如果我想要来自表 c 和 o 的数据怎么办？

var query = from c in context.Contacts
            join o in context.Orders on c.Id on o.CustomerId
            //insert answer here
            select new { g.Key, g.Sum(c => c.Whatever), g.Sum(o => o.Whatever) };

这甚至可能吗？

Answer 1

var query = from c in context.Contacts
            join o in context.Orders on c.Id equals o.CustomerId
            select new 
            { 
                Contact = c, 
                Order = o 
            } into ContactAndOrder
            group ContactAndOrder by ContactAndOrder.Order.Id into g
            select new 
            { 
                g.Key, 
                ContactWhatever = g.Sum(co => co.Contact.Whatever), 
                OrderWhatever = g.Sum(co => co.Order.Whatever) 
            };