LinQ：具有多个列标识符的多个连接(LinQ: Multiple joins with multiple columns identifiers)

 你能帮我理解这个错误信息吗？ 我确实做错了什么但是什么？ 
 
 join子句中某个表达式的类型不正确。 调用“加入”时类型推断失败。 
 
Res.AddRange(from jh in db.Job
             join jd in db.JobDetail on jh.number equals jd.number
             join js in db.JobSection on new { jd.number, jd.ref, jd.product } equals new { js.number, js.ref, js.Product }
             join oh in db.Order on jd.ref equals oh.ref
             join bh in db.Buyer on jh.id equals bh.id
             where jh.dateModify >= InputDate
             select jh);
 
 错误来自这一行 
 
join js in db.JobSection on new { jd.number, jd.ref, jd.product } equals new { js.number, js.ref, js.Product }

Could you help me to understand this error message. I did something wrong for sure but what?
 
The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'Join'.
 
Res.AddRange(from jh in db.Job
             join jd in db.JobDetail on jh.number equals jd.number
             join js in db.JobSection on new { jd.number, jd.ref, jd.product } equals new { js.number, js.ref, js.Product }
             join oh in db.Order on jd.ref equals oh.ref
             join bh in db.Buyer on jh.id equals bh.id
             where jh.dateModify >= InputDate
             select jh);
 
The error come from this line 
 
join js in db.JobSection on new { jd.number, jd.ref, jd.product } equals new { js.number, js.ref, js.Product }

原文：https://stackoverflow.com/questions/37698692