public Estudiante UpdateStudent(string id, Estudiante s)
 {
     Estudiante p = objStudent.FirstOrDefault(e => e.ID.Equals(id));
     p.birthdate = s.birthdate;
     p.firstname = s.firstname;
     p.lastname = s.lastname;
     p.idbooster = s.idbooster;
     return p;
 }
 public Estudiante CreateStudent(Estudiante s)
 {
     s.ID = (++studentCount).ToString();
     objStudent.Add(s);
     return s;
 }