System.Xml.DtdParser.ParseUnexpectedToken C# (CSharp) Method

        private string ParseUnexpectedToken(int startPos)
        {
            if (_xmlCharType.IsNCNameSingleChar(_chars[startPos])
#if XML10_FIFTH_EDITION
                || xmlCharType.IsNCNameHighSurrogateChar( chars[startPos] ) 
#endif
                )
            { // postpone the proper surrogate checking to the loop below
                int endPos = startPos;
                for (;;)
                {
                    if (_xmlCharType.IsNCNameSingleChar(_chars[endPos]))
                    {
                        endPos++;
                    }
#if XML10_FIFTH_EDITION
                    else if ( chars[endPos] != 0 && // check for end of the buffer
                              xmlCharType.IsNCNameSurrogateChar( chars[endPos], chars[endPos + 1] ) ) {
                        endPos += 2;
                    }
#endif
                    else
                    {
                        break;
                    }
                }
                int len = endPos - startPos;
                return new string(_chars, startPos, len > 0 ? len : 1);
            }
            else
            {
                Debug.Assert(startPos < _charsUsed);
                return new string(_chars, startPos, 1);
            }
        }