partial void DeleteBooks(Books instance);
 partial void UpdateBooks(Books instance);
 private void detach_Books(Books entity)
 {
     this.SendPropertyChanging();
     entity.BookCategories = null;
 }
 partial void InsertBooks(Books instance);
 private void attach_Books(Books entity)
 {
     this.SendPropertyChanging();
     entity.BookCategories = this;
 }