LINQ OrderBy通过联接表中的记录计数

Question

我在将以下tSQL转换为C＃中的LINQ to SQL时遇到问题。 任何帮助将非常感激：

SELECT P.Name
FROM Product P
    INNER JOIN OrderItems OI ON P.productID = OI.productID
        INNER JOIN Orders O ON OI.orderID = O.orderId
WHERE P.Active = 1 AND O.Status > 2
ORDER BY count(OI.orderID) DESC

这是由JOINED表的COUNT排序导致的循环。

这是我到目前为止（没有订单）：

from p in CRM.tProducts
    join oi in CRM.tOrderItems on p.prodID equals oi.prodID
    join o in CRM.tOrders on oi.orderID equals o.orderID
where o.status > 1 && p.active == true
select p;

谢谢你的帮助！

Answer 1

如果需要计数，则需要执行一个分组

SELECT P.Name
FROM Product P
    INNER JOIN OrderItems OI ON P.productID = OI.productID
        INNER JOIN Orders O ON OI.orderID = O.orderId
WHERE P.Active = 1 AND O.Status > 2
GROUP BY P.Name
ORDER BY count(*) DESC

我假设您实际上想要投影中每个组的计数。

from p in CRM.tProducts
    join oi in CRM.tOrderItems on p.prodID equals oi.prodID
    join o in CRM.tOrders on oi.orderID equals o.orderID
where o.status > 1 && p.active == true
group p by p.Name into nameGroup
orderby nameGroup.Count()
select new { Name = nameGroup.Key, Count = nameGroup.Count() };

Answer 2

请参阅评论评论。

如何在Linq中执行“排序依据”->

如果你有

  var alist = ....  select new { prd = p, ord =  o };

你可以做

  alist.sort( (a, b) => a.ord.CompareTo(b.ord) );

将它排序到位。