날짜 문자열 엑셀 날짜코드로 변환 C#

string dateString = "2023-05-09"; 
DateTime dateTime = DateTime.ParseExact(dateString, "yyyy-MM-dd", null); 
DateTime excelDateTime = new DateTime(1899, 12, 30); 
double excelDateCode = (dateTime - excelDateTime).TotalDays + 2;