Linq(ef)の添削の文法

//        
  using (StudentDbEntities db = new StudentDbEntities())
            {
            //  
                var avb = db.Student.Include("grade1").Select(s => new
                {
                    id = s.id,
                    name = s.name,
                    age = s.age,
                    //gradnaem          
                   //grade1  ef                   
                    gradnaem = s.grade1.gradename//     grade1.             



                }).ToList();
                dataGridView1.DataSource = avb;
            }

  public static  bool  Add(Student student) {
            using (StudentDbEntities db=new StudentDbEntities())
            {
                db.Student.Add(student);
                return db.SaveChanges() > 0;
            }
        }

 public static bool delete(int id) {
            using (StudentDbEntities db=new StudentDbEntities())
            {
                var sc = db.Student.FirstOrDefault(s => s.id == id);
                db.Student.Remove(sc);
             return  db.SaveChanges()>0;

            }
        
        }