Escape markdown tokens for Telegram markdown markup

EscapeMarkdown.cs

// Does it work properly with utf16 encoded strings (utf16 is used in .NET internally)
// considering that its length is two bytes and strings are iterated char by char?
public static class StringExtensions
{
    private static char[] EscapableChars = { '*', '_', '[', '`', '\\', ']' };

    public static string EscapeMarkdown(this string value)
        => string.Join(
            string.Empty,
            value.Select(
                character => EscapableChars.Contains(character)
                    ? $"\\{character}"
                    : $"{character}"));
}

EscapeMarkdown2.cs

// Regex version
public static class StringExtensions
{
    public static string EscapeMarkdown(this string input)
        => Regex.Replace(
            input,
            "(?<token>[*_\\\\`\\\\[\\]])",
            m => $"\\{m.Groups["token"].Value}");
}