Various ways of sanitizing XML input

gistfile1.txt

/// http://seattlesoftware.wordpress.com/2008/09/11/hexadecimal-value-0-is-an-invalid-character/
/// http://stackoverflow.com/questions/157646/best-way-to-encode-text-data-for-xml/732135#732135

public string Clean(string text)
{
    return new string(text.Where(XmlConvert.IsXmlChar).ToArray());
}
        
public static string CleanInvalidXmlChars(string text)
{
    // From xml spec valid chars:
    // #x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD] | [#x10000-#x10FFFF]    
    // any Unicode character, excluding the surrogate blocks, FFFE, and FFFF.
    string re = @"[^\x09\x0A\x0D\x20-\xD7FF\xE000-\xFFFD\x10000-x10FFFF]";
    return Regex.Replace(text, re, "");
}




private string SanitizeXmlString(string xml)
{
    if (xml == null)
    {
        throw new ArgumentNullException("xml");
    }

    var buffer = new StringBuilder(xml.Length);

    foreach (char c in xml)
    {
        if (IsLegalXmlChar(c))
        {
            buffer.Append(c);
        }
    }

    return buffer.ToString();
}

private bool IsLegalXmlChar(int character)
{
    return
    (
         character == 0x9 /* == '\t' == 9   */          ||
         character == 0xA /* == '\n' == 10  */          ||
         character == 0xD /* == '\r' == 13  */          ||
        (character >= 0x20 && character <= 0xD7FF) ||
        (character >= 0xE000 && character <= 0xFFFD) ||
        (character >= 0x10000 && character <= 0x10FFFF)
    );
}