c# - 如何在LINQ Join中使用AND

我正在尝试将SQL查询转换为linq，但不像在本示例SQL查询中那样，不知道如何在join语句内使用AND子句。

我在下面突出了我无法弄清的部分。

DECLARE @GroupId INT = 10

SELECT
    U.UserName,
    U.UserID,
    @GroupId AS "GroupID",
    CASE WHEN GU.GROUPID IS NULL THEN 0
         ELSE 1 END
         AS InGroup
FROM Users U
LEFT JOIN GroupUsers GU on GU.UserID = U.UserID
    AND GU.GROUPID = @GroupId -- HERE!!

这跟我已经接近

from user in Users
join gu in GroupUsers on user.UserID equals gu.UserID into subq
from sub in subq.DefaultIfEmpty()
where sub.GroupID == 10 || sub == null
select new
{
    Username = user.UserName,
    UserId = user.UserID,
    GroupId = 10,
    InGroup = sub != null
}

但它使用WHERE删除数据。

最佳答案

您可以将GroupId条件嵌入查询中：

 from user in Users
 join gu in GroupUsers.Where(gu => gu.GroupID == 10)
    on user.UserID equals gu.UserID into subq
 from sub in subq.DefaultIfEmpty()
 select new
 {
     Username = user.UserName,
     UserId = user.UserID,
     GroupId = 10,
     InGroup = sub != null
 }

关于c# - 如何在LINQ Join中使用AND，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/26060228/