Question

我可以这样查询吗？

var result = from us20 in Us20Repository.GetAll()
             join pj01 in Pj01Repository.GetAll() on new
             {
                User =
                    (us20.company == "kodofisi" ?
                        us20.personalId :
                        (
                            us20.company == "coca-cola" ?
                            (
                                (from pj02 in Pj02Repository.GetAll()
                                where
                                    pj02.id == us20.id &&
                                    pj02.personalId == us20.personalId
                                select new
                                {
                                    pj02.id
                                }).First().ToString()
                            ) :
                            ""
                        )
                    ),
                ACTIVE = "X"
             } equals new { User = pj01.name, ACTIVE = pj01.active }
             select new
             {
                 Name = pj01.id
             };

这在加入时不起作用，如何使用select来完成？数据没有来。

相应的查询是否有效：

/*bla bla*/ FROM us20 US20
INNER JOIN pj01 PJ01 ON PJ01.PJID = 
( 
    CASE WHEN (US20.company = "kodofisi") 
    THEN 
        US20.personalId 
    WHEN
        (US20.BKNM = "coca-cola")
    THEN
        (
            SELECT dataId FROM pj02 WHERE id = US20.id AND personalId = US20.personalId
        ) END 
) AND PJ01.active = "X"

Answer 1

我不知道这是否是造成问题的原因，但也许您可以尝试在代码段上使用FirstOrDefault（）而不是First（）：

(from pj02 in Pj02Repository.GetAll()
                            where
                                pj02.id == us20.id &&
                                pj02.personalId == us20.personalId
                            select new
                            {
                                pj02.id
                            }).First().ToString()

这种变化解决了我遇到的类似问题。

如何做C＃Linq加入等于哪里

1 个答案: