Convert UT8 to GB2312 (Chinese Encoding)

            string GBInfo = string.Empty;
            Encoding utf8 = Encoding.UTF8;
            Encoding gb2312 = Encoding.GetEncoding("gb2312");
            byte[] UnicodeBytes = utf8.GetBytes(str);
            byte[] AscIIBytes = Encoding.Convert(utf8, gb2312, UnicodeBytes);
            char[] AscIIChars = new char[gb2312.GetCharCount(AscIIBytes, 0,   
            AscIIBytes.Length)];
            gb2312.GetChars(AscIIBytes, 0, AscIIBytes.Length, AscIIChars, 0);
            return AscIIBytes;