public static string ConvertExtendedASCII(string HTML)

{

    StringBuilder str = new StringBuilder();

    char c;

    for (int i = ; i < HTML.Length; i++)

    {

        c = HTML[i];

        if (Convert.ToInt32(c) > )

        {

            str.Append("&#" + Convert.ToInt32(c) + ";");

        }

        else

        {

            str.Append(c);

        }

    }

    return str.ToString();

}