public IActionResult Checkout(Guid orderId, Guid userId) { var itemsNotInStock = orderManager.IsOrderInStock(orderId); if (itemsNotInStock.Any()) { return(BadRequest($"Sorry these items are out of stock : " + string.Join(",", itemsNotInStock.ToArray()))); } orderManager.PlaceOrder(orderId); userManager.AddOrder(userId, orderId); return(Ok()); }