public static ValidatableCustomOrder Get(int orderID)
    {
        ValidatableCustomOrder loadedOrder = LoadOrderFromSomewhere(orderID);
        ValidatableCustomOrder copiedOrder = new ValidatableCustomOrder(loadedOrder);

        return copiedOrder
    }
 public ValidatableCustomOrder(ValidatableCustomOrder copiedOrder)
     : base(copiedOrder)
 {
     this.IsValid = copiedOrder.IsValid;
 }