A persistence format of your own

The format

The simplest honest persistence format is line-oriented: one record per line, fields separated by a delimiter chosen to never appear in the data:

// save: id|name|score
File.WriteAllLines(path, players.Select(p => $"{p.Id}|{p.Name}|{p.Score}"));

Loading is the mirror:

foreach (string line in File.ReadAllLines(path))
{
    string[] parts = line.Split('|');
    players.Add(new Player(int.Parse(parts[0]), parts[1], int.Parse(parts[2])));
}

Design honestly, test both directions

Choose | (or tab) over , when your data is free text — commas live inside prose. Decide the corrupt-line policy before it happens: skip-and-count, or fail loudly? Round-trip testing is the non-negotiable part: save, load, assert equal. If a format can't survive its own save/load cycle, nothing built on it can.