public static List<User> LoadUsers()
    {
        List<User> users = new List<User>();
        var dataLines = ReadLines(config["users"]);

        foreach (var line in dataLines)
        {
            var args = line.Split(new string[] { ";" }, StringSplitOptions.RemoveEmptyEntries);
            var id = int.Parse(args[0]);
            var username = args[1];
            var password = args[2];
            var postIds = args[3]
                .Split(new string[] { "," }, StringSplitOptions.RemoveEmptyEntries)
                .Select(int.Parse)
                    .ToArray();
            User user = new User(id, username, password, postIds);
            users.Add(user);
        }

        return users;
    }

    public static void SaveUsers(List<User> users)
    {
        List<string> lines = new List<string>();

        foreach (var user in users)
        {
            const string userFormat = "{0};{1};{2};{3}";
            string line = string.Format(userFormat,
                user.Id,
                user.Username,
                user.Password,
                string.Join(",", user.PostIds)
            );

            lines.Add(line);
        }
        WriteLines(config["users"], lines.ToArray());
    }

    public static List<Post> LoadPosts()
    {
        List<Post> posts = new List<Post>();
        var dataLines = ReadLines(config["posts"]);

        foreach (var line in dataLines)
        {
            var args = line.Split(new string[] { ";" }, StringSplitOptions.RemoveEmptyEntries);
            var id = int.Parse(args[0]);
            var title = args[1];
            var content = args[2];
            var categoryId = int.Parse(args[3]);
            var authorId = int.Parse(args[4]);

            var replyIds = args[5]
                .Split(new string[] { "," }, StringSplitOptions.RemoveEmptyEntries)
                .Select(int.Parse)
                    .ToArray();
            Post post = new Post(id, title, content, categoryId, authorId, replyIds);
            posts.Add(post);
        }

        return posts;
    }

    public static void SavePosts(List<Post> posts)
    {
        List<string> lines = new List<string>();

        foreach (var post in posts)
        {
            const string postFormat = "{0};{1};{2};{3};{4};{5}";
            string line = string.Format(postFormat,
                post.Id,
                post.Title,
                post.Content,
                post.CategoryId,
                post.AuthorId,
                string.Join(",", post.ReplyIds)
            );

            lines.Add(line);
        }
        WriteLines(config["users"], lines.ToArray());
    }