public ShoppingList Load_ShoppingList(string user_id, string shoppingList_id)
        {
            ShoppingList list = null;

            try
            {
                string file_path =
                    System.IO.Path.Combine(_filesystemService.GetUserFolderPath(user_id), shoppingList_id + ".json");

                if (File.Exists(file_path))
                {
                    string file_content = File.ReadAllText(file_path);
                    list = JsonConvert.DeserializeObject <ShoppingList>(file_content);
                }
                else
                {
                    Console.Error.WriteLine("Load_ShoppingList: list not found at " + file_path);
                }
            }
            catch (Exception ex)
            {
                Console.Error.WriteLine("Load_ShoppingList " + ex);
            }
            return(list);
        }