bool IsLegalXmlChar(int character) => character == 0x9 /* == '\t' == 9 */||
character == 0xA /* == '\n' == 10 */||
character == 0xD /* == '\r' == 13 */||
(character >= 0x20 && character <= 0xD7FF) ||
(character >= 0xE000 && character <= 0xFFFD) ||
(character >= 0x10000 && character <= 0x10FFFF);
}