public void AddRecord(Student t)
 {
     using (SchoolDbEntities db = new SchoolDbEntities())
     {
         db.Students.Add(t);
         db.SaveChanges();
     }
 }
        public void DeleteRecord(int id)
        {
            using (SchoolDbEntities db = new SchoolDbEntities())
            {
                var d = db.Students.Where(s => s.Id == id).FirstOrDefault();

                db.Students.Remove(d);
                db.SaveChanges();
            }
        }