Code 128 font (barcode) code in C#

I have problem using code128 barcode font.
When I use character 154 (& #154) in html it will be š but in C# its wrong.
š value will be 353 in C#.
So I make table for the character.
here's the codes:

        readonly static string code128AsciiTable = "€!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~‘’“”•–—˜™š›œ";
        private char Code128ToAscii(char c)
        {
            char res = (char)code128AsciiTable[(int)c];
            return res;
        }
        private char AsciiToCode128(char c)
        {
            char res = (char)code128AsciiTable.IndexOf(c);
            return res;
        }
        private char Code128CheckSum( string str, char startChar )
        {
            int result = 0;
            for (int i = 0; i < str.Length; ++i)
            {
                result += (int)str[i] * (i + 1);
            }
            result += (int)startChar;
            result %= 103;
            result = Code128ToAscii((char)result);
            return (char)result;
        }
        public string ConvertToCode128Format(string str)
        {
            char startChar = code128AsciiTable[104];
            char stopChar = code128AsciiTable[106];
            string convertedStr = "";
            for (int i = 0; i < str.Length; ++i)
            {
                convertedStr += AsciiToCode128(str[i]);
            }
            char checkSum = Code128CheckSum(convertedStr, (char)104);
            string FullConvert = startChar + str + checkSum + stopChar;
            return FullConvert;
        }
        public void Test()
        {
            string testString = "156461003";
            string code128String = ConvertToCode128Format(testString);
        }