private bool FilterOrder_Details(Order_Detail entity)
 {
     return (entity.ProductID == this.ProductID);
 }
 private void DetachOrder_Details(Order_Detail entity)
 {
     entity.Product = null;
 }
 private void AttachOrder_Details(Order_Detail entity)
 {
     entity.Product = this;
 }
 private bool FilterOrder_Details(Order_Detail entity)
 {
     return (entity.OrderID == this.OrderID);
 }
 private void DetachOrder_Details(Order_Detail entity)
 {
     entity.Order = null;
 }
 private void AttachOrder_Details(Order_Detail entity)
 {
     entity.Order = this;
 }