show sevaral row with one forign key in datagrid using EF

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C#

entity-framework

hi i use this code for fill datagrid (EF)
i use many to many relashion...
but when one kelas have several teacher, datagrid show several row of class for any teacher
i want to show any class with teachers in one row wit comma separate for teacher
can any one help me?

var q = from p1 in db.tbl_dore
                    join p2 in db.tbl_dore_teacher on p1.dore_id equals p2.fk_dore into list1
                    from l1 in list1.DefaultIfEmpty()
                    join p3 in db.tbl_teacher on l1.fk_teacher equals p3.teacher_id into list2
                    from l2 in list2.DefaultIfEmpty()
                    select new {p1.dore_id, p1.dore_code,p1.dore_startdate,l2.teacher_fullname} ;
           dgv_dore.DataSource = q.ToList();

kelas teacher
1 A
1 B
2 C

i want to ...
kelas teacher
1 A,B
2 C

thanks