Checking For Edited File

i Wanted To Get one image From Server(Offline game) And Keep For Loading Offline. But I’m Changing That Image Time to Time So I Want To Know Image Changed To Download It Again. Ho To Know the Image Changed Or Not?

Use a bool value to be sent from where you are changing the image ( that function). Use this bool value in if to check.
It will be easier to explain if you had actually given the code snippet.