partial void DeleteStudent_Class(Student_Class instance);
 partial void UpdateStudent_Class(Student_Class instance);
 private void detach_Student_Class(Student_Class entity)
 {
     this.SendPropertyChanging();
     entity.ClassInfo = null;
 }
 partial void InsertStudent_Class(Student_Class instance);
 private void attach_Student_Class(Student_Class entity)
 {
     this.SendPropertyChanging();
     entity.Student = this;
 }