C# 如何通过linq在join语句中使用两个条件？

我试图在我的连接中添加两个条件，但我做不到。我使用| |运算符

from pay in db.Payments
join FlyRpt in db.FlightReportTickets 
on pay.ObjectIdDepartue equals FlyRpt.DepartureId ||
   FlyRpt.DepartureId equals pay.ObjectIdReturn

join prof in db.Profiles on FlyRpt.UserId equals prof.UserId
where pay.ReserveType == 1 &&
    pay.Transactionsuccess &&
    pay.IssueDate >= fromDateTime &&
    pay.IssueDate <= toDateTime

select new
{
    FlyRpt.FullPrice
};

---

如果要实施或加入，则需要使用where：

from pay in db.Payments
from FlyRpt in db.FlightReportTickets
where pay.ObjectIdDepartue == FlyRpt.DepartureId
|| FlyRpt.DepartureId == pay.ObjectIdReturn
join prof in db.Profiles on FlyRpt.UserId equals prof.UserId
where pay.ReserveType == 1 &&
pay.Transactionsuccess &&
pay.IssueDate >= fromDateTime &&
pay.IssueDate <= toDateTime
select new
{
    FlyRpt.FullPrice,
};

---

可以使用交叉联接，因为不能在其他联接中使用或：

from pay in db.Payments
from FlyRpt in db.FlightReportTickets 
where 
    pay.ObjectIdDepartue = FlyRpt.DepartureId ||
    FlyRpt.DepartureId equals pay.ObjectIdReturn
join prof in db.Profiles 
on FlyRpt.UserId equals prof.UserId
where 
    pay.ReserveType == 1 &&
    pay.Transactionsuccess &&
    pay.IssueDate >= fromDateTime &&
    pay.IssueDate <= toDateTime
select new
{
    FlyRpt.FullPrice,
};

---

或操作……错误消息是什么？无法将运算符| |应用于System.Nullable和System.Nullable类型的操作数