public void Save(){
    //validate
    if (this.OrderItems.Count == 0)
        throw new Exception ("You need at least one order item");

    //so the user code does not have to do this
    this.DateTimeModified = DateTime.Now;

    saveToDataBase();

    //after saving to the DB, the order amount is greater than $3000, notify certain people
    if (OrderAmount >= 3000)
        notifyPersonell();
}

order.ValidateOrder();
context.SaveChanges();
order.AfterOrderChanged();