C# LINQ 分组依据和选择集合
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LINQ Group By and select collection
提问by jenson-button-event
I have this structure
我有这个结构
Customer
- has many Orders
- has many OrderItems
I want to generate a list of CustomerItemsvia LINQ given a subset of OrderItems:
我想CustomerItems通过给定以下子集的 LINQ生成一个列表OrderItems：
List of new { Customer, List<OrderItem> Items }
which is a grouping of all the items a Customer has ordered from the subset of items
这是客户从项目子集中订购的所有项目的分组
How can i use LINQ to back track through the order and group by Customer to generate this object?
如何使用 LINQ 回溯订单和客户分组以生成此对象？
so far I'm on something like
到目前为止，我正在做类似的事情
items
.GroupBy(i => i, i => i.Order.Customer, (i, customer) => new {customer, i})
But thats obviously not a List. I'm guessing I need a SelectMany in there somewhere, but could do with some pointers.
但这显然不是一个列表。我猜我在某个地方需要一个 SelectMany，但可以使用一些指针。
采纳答案by Ani
I think you want:
我想你想要：
items.GroupBy(item => item.Order.Customer)
.Select(group => new { Customer = group.Key, Items = group.ToList() })
.ToList()
If you want to continue use the overload of GroupByyou are currently using, you can do:
如果您想继续使用GroupBy您当前正在使用的重载，您可以执行以下操作：
items.GroupBy(item => item.Order.Customer,
(key, group) => new { Customer = key, Items = group.ToList() })
.ToList()
...but I personally find that less clear.
...但我个人觉得不太清楚。
回答by cimey
you can achive it with group join
你可以通过组加入来实现它
var result = (from c in Customers
join oi in OrderItems on c.Id equals oi.Order.Customer.Id into g
Select new { customer = c, orderItems = g});
c is Customer and g is the customers order items.
c 是客户，g 是客户订购的商品。
回答by caras
you may also like this
你可能也喜欢这个
var Grp = Model.GroupBy(item => item.Order.Customer)
.Select(group => new
{
Customer = Model.First().Customer,
CustomerId= group.Key,
Orders= group.ToList()
})
.ToList();
