I'm trying write this sql query to Linq:

**SQL:**

```
select c.course_name, count(s.s_name) as studenti from course c 
join study_group g on g.course_id=c.id 
join student s on s.study_group_id=g.id 
group by c.course_name;

```

**Linq:**

```
var countStudents = (from s in ado.student //on g.id equals s.study_group_id
                     join g in ado.study_group on s.study_group_id equals g.id
                     join c in ado.course on g.course_id equals c.id
                     group s by c.course_name into cn
                     let count = cn.Count(co => co.s_name)
                     select new 
                     {
                        c.course_name
                        course_name = cn.Key
                     });

```

and still I have an error at `co => co.s_name`

Error: `Cannot implicitly convert type 'string' to 'bool'`

Know anybody how to fix this ?

Thank you.