林克查詢與內部選擇在EF的兩個連接

Question

我試圖創建一個Linq查詢EF連接2內部選擇的值。下面你會發現的SQL查詢做的伎倆，試圖在LINQ to做，當事情更加棘手。

我使用POCO對象，並希望查詢返回列表而不是匿名類型。這可能與LINQ到EF？

 
SELECT s1.* 
FROM [Statistics] s1 
INNER JOIN 
(
    SELECT MAX(CreateDate) as createdate 
    FROM [Statistics] 
    GROUP BY UserId 
) s2 
ON s1.UserId = s2.[UserId] and s1.CreateDate = s2.createdate 
ORDER BY s1.Balance desc 

Answer 1

您可以通過Where或Join進行此操作。

from s1 in Statistics 
join s2 in (from s in Statistics group s by s.UserId into g 
select new { UserId = g.Key, CreateDate = g.Max (s => s.CreateDate) }) 
on new { s1.UserId, s1.CreateDate } equals new { s2.UserId, s2.CreateDate } 
orderby s1.Balance descending 
select s1; 

或者，

from s1 in Statistics 
from s2 in (from s in Statistics group s by s.UserId into g 
select new { UserId = g.Key, CreateDate = g.Max (s => s.CreateDate) }) 
where s1.UserId == s2.UserId && s1.CreateDate == s2.CreateDate 
orderby s1.Balance descending 
select s1;