System.Net.WebUtility.IndexOfHtmlEncodingChars C# (CSharp) Method

        private static unsafe int IndexOfHtmlEncodingChars(string s, int startPos)
        {
            Debug.Assert(0 <= startPos && startPos <= s.Length, "0 <= startPos && startPos <= s.Length");

            int cch = s.Length - startPos;
            fixed (char* str = s)
            {
                for (char* pch = &str[startPos]; cch > 0; pch++, cch--)
                {
                    char ch = *pch;
                    if (ch <= '>')
                    {
                        switch (ch)
                        {
                            case '<':
                            case '>':
                            case '"':
                            case '\'':
                            case '&':
                                return s.Length - cch;
                        }
                    }
#if ENTITY_ENCODE_HIGH_ASCII_CHARS
                    else if (ch >= 160 && ch < 256)
                    {
                        return s.Length - cch;
                    }
#endif // ENTITY_ENCODE_HIGH_ASCII_CHARS
                    else if (Char.IsSurrogate(ch))
                    {
                        return s.Length - cch;
                    }
                }
            }

            return -1;
        }