Based on my knowledge i am providing suggestion below. just check if it is useful to you.
i think we cannot directly give YYYYMMDD in search criteria.
you are checking all the files with the format of YYYYMMDD right. try to get the current year and current month dynamically from the functions like Current Year - now.toString(“YYYY”).tostring and current Month - Now.tostring(“MM”).tostring. and pass it to your search criteria like below.
ile = Directory.GetFiles(“PathFile”,CurrentYear+CurrentMonth+“*_Report.xls”, SearchOption.AllDirectories) some thing like this it should work and take correct files and ignore the rest of ones.