Is there a not in sub-query for Linq to Enties as in this T-SQL

Question

Assume the classic self-referencing Employee table where each employee may have at most one ReportsTo, as created with this T-SQL snippet and sample data:

create table Employees
(
    Id          int identity primary key,
    Name        nvarchar(30),
    Region      nvarchar(10),
    ReportsTo   int null
        foreign key(ReportsTo) references Employees(Id)
)

insert into Employees values('Boss','HO',null)
insert into Employees values('Underling', 'HO',
        (select Id from Employees where Name='Boss'))
insert into Employees values('Self Important', 'Region 1',
        (select Id from Employees where Name='Underling'))
insert into Employees values('Very Underling', 'Region 1',
        (select Id from Employees where Name='Self Important'))

I can select the manager for Region 1 with this T-SQL

select * from Employees 
where Region = 'Region 1' and 
ReportsTo not in (select Id from Employees where Region = 'Region 1')

In other words, the manager is an employee with not reports to in his region.

Now, how do I determine the manager for Region 1 using Linq?

Answer 1

How about something like this:

from e in context.Employee
where e.Region == "Region 1" 
&& !(from e2 in context.Employee
     where e2.Region == "Region 1"
     select e2.Id).ToList().Contains(e.ReportsTo)
select e;

Answer 2

I believe you can query within queries through Linq. It looks like the below

db.Employees.Where(u => u.Region = 'Whatever').Where(u =>
    db.Employees
    .Where(v => ReportsTo <> 'Whatever')
    .Select(v => v.Id)
    .Contains(u.Id)
)

this may need some work before it's ready to go, but I think that's the general idea