Time difference C#

I try to create app . scenario is i have a folder in that folder there is some files so every file is taking update in every 15 mint check image 

 there is 3 files so every file update in every 5 seconds when this fully update then next file is create so i want when there is no update in file in every 5 seconds then i want to insert data in table otherwise not

when i try this and when i set breakpoint i see that within 5 seconds data is send to table where as i want after seconds data is send to table when there is no update in file any solution