C# Linq 多级连接表

Question

我正在尝试查询 3 级表 ef_staff 表 3 次，以获取每行的 3 个差异人员对象。如何在 LINQ 中翻译这个？

SELECT a.a_appraisalid, a.a_year, c.s_staffName, c2.s_staffName, c3.s_staffName
FROM   ef_appraisal a, idp_application b, ef_staff c, ef_staff c2, ef_staff c3
WHERE  a.a_appraisalid = b.a_appraisalid AND
       a.a_staffid = c.s_staffid AND
       a.a_appraisedby = c2.s_staffid AND
       a.a_reviewedby = c3.s_staffid

我尝试了很多方法，但在第 2 次和第 3 次加入 Staff 时仍然出现“Type Inference Failed”错误。我在这里缺少什么？

from application in applications

join appraisal in pmsEntities.ef_appraisal on application.a_appraisalid equals appraisal.a_appraisalid

join staff in pmsEntities.ef_staff on appraisal.a_staffid equals staff.s_staffid

join appraiser in pmsEntities.ef_staff on staff.s_appraisedby equals appraiser.s_staffid into ap

from appraiser in ap.DefaultIfEmpty() 

join reviewer in pmsEntities.ef_staff on staff.s_reviewedby equals reviewer.s_staffid into rv

from reviewer in rv.DefaultIfEmpty() 

join company in pmsEntities.ef_company on appraisal.a_companyid equals company.c_companyid into jc

from company in jc.DefaultIfEmpty()

select appraisal, staff.staffName, appraiser.staffName, reviewer.staffName, company.compName

Answer 1

我改正了错误。员工对象的第一级加入应链接到员工对象的第二级，如下所示:

加入 staff in pmsEntities.ef_staff on appraisal.a_staffid equals staff.s_staffid into staffj

                    from staff1 in staffj

                    join appraiser in pmsEntities.ef_staff on staff1.s_appraisedby equals appraiser.s_icno into staff2

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