void BuyProduct <AdminMethod>(string username, string prodID, string nulc)
        {
            User    user;
            Product product;

            try
            {
                user = GetUser(username);
                int id = Convert.ToInt32(prodID);
                product = Stregsystem.GetProductByID(id);
                BuyTransaction tr = Stregsystem.BuyProduct(user, product);
                UI.DisplayUserBuysProduct(tr);
            }
            catch (UserNotFoundException e)
            {
                UI.DisplayUserNotFound(e.username);
            }
            catch (InsufficientCreditsException e)
            {
                UI.DisplayInsufficientCash(e.user, e.product);
            }
            catch (ProductNotActivatedException e)
            {
                UI.DisplayProductNotActivated(e.product);
            }
            catch (ProductNotFoundException)
            {
                UI.DisplayProductNotFound(prodID);
            }
            catch (FormatException)
            {
                UI.DisplayQuantityMustBeANumber();
            }
            catch (OverflowException)
            {
                UI.DisplayQuantityMustBeANumber();
            }
            catch (Exception e)
            {
                UI.DisplayGeneralError(e.Message);
            }
        }