public static void ShowItemsByPriceInterval(ref RestaurantManager restaurantManager) { Console.WriteLine("Enter the first price:"); string firstPriceStr = Console.ReadLine(); double firstPrice; while (!double.TryParse(firstPriceStr, out firstPrice) || firstPrice < 0) { Console.WriteLine("Error! Enter the price correctly!"); firstPriceStr = Console.ReadLine(); } Console.WriteLine("Enter the second price:"); string secondPriceStr = Console.ReadLine(); double secondPrice; while (!double.TryParse(secondPriceStr, out secondPrice) || secondPrice < 0) { Console.WriteLine("Error! Enter the price correctly!"); secondPriceStr = Console.ReadLine(); } List <MenuItem> itemsCategory = restaurantManager.GetMenuItemsPriceInterval(firstPrice, secondPrice); foreach (var item in itemsCategory) { Console.WriteLine($"Name; {item.Name}\nNo: {item.Name}\nCategory: {item.Category}\nPrice: {item.Price}"); } }