partial void Deleteguardian(guardian instance);
 partial void Updateguardian(guardian instance);
 private void detach_guardians(guardian entity)
 {
     this.SendPropertyChanging();
     entity.student = null;
 }
 partial void Insertguardian(guardian instance);
 private void attach_guardians(guardian entity)
 {
     this.SendPropertyChanging();
     entity.student = this;
 }