IOHelper.cs

public static class IOHelper
{
    public static void ListDirsOnDir(string dir)
    {
        if (!Directory.Exists(dir))
            return;

        string[] dirs = Directory.GetDirectories(dir);
        foreach (var d in dirs)
            ListDirsOnDir(d);

        string[] files = Directory.GetFiles(dir);
        foreach (var file in files)
            Debug.Log(file);
    }
}