SQL 的not in 如何转化成LINQ ?泪奔求高手解答！

SQL 的not in 怎么转化成LINQ ?泪奔求高手解答！！！！！
有高手吗

C# code

select * from QY_Business where BusinessID not in(select OtherBusinessID from QY_BusinessAssignConsumePlaceDetail) 

C# code

var result=from u in db. QY_Business           let n =QY_BusinessAssignConsumePlaceDetail.select(c=>c.OtherBusinessID )           where !n.Contains(u.BusinessID)           select u;