Co-related Queries using lambda expressions - linq

Question

How can I convert this LINQ query from query syntax to method syntax? I am performing a co-related query operation.
var query = (from r in objEntities.Employee
where r.Location == (from q in objEntities.Department
where q.Location == r.Location
select q.Location).FirstOrDefault()
select new
{
FirstName = r.FirstName,
LastName = r.LastName,
Age = r.Age,
Location = r.Location
});
GridView1.DataSource = query;
GridView1.DataBind();

Answer 1

I think you are trying to convert the query to method-based query instead of syntax-based query.
var query = objEntities.Employee
.Where(e => e.Location == objEntities.Department
.Where(d => d.Location == r.Location)
.Select(d => d.Location)
.FirstOrDefault())
.Select(e => new {
FirstName = e.FirstName,
LastName = e.LastName,
Age = e.Age,
Location = e.Location
});
I'm also pretty sure your inner expression within where clause could be replaced with something like that:
.Where(e => objEntities.Department.Any(d => d.Location == e.Location)

Answer 2

Nested queries always have performance issue instead you should use join:
In the lambda expression query should be
var query = objEntities.Employee.Join(objEntities.Department, E => E.Location,
D => D.Location,
(E,D) => new {
FirstName = E.FirstName,
LastName = E.LastName,
Age = E.Age,
Location = E.Location
});