Home/ Questions/Q 8281715
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-08T10:07:51+00:00

I need to uniquely identify a file on Windows so I can always have

  • 0

I need to uniquely identify a file on Windows so I can always have a reference for that file even if it’s moved or renamed. I did some research and found the question Unique file identifier in windows with a way that uses the method GetFileInformationByHandle with C++, but apparently that only works for NTFS partitions, but not for the FAT ones.

I need to program a behavior like the one on DropBox: if you close it on your computer, rename a file and open it again it detects that change and syncs correctly. I wonder whats the technique and maybe how DropBox does if you guys know.

FileSystemWatcher for example would work, but If the program using it is closed, no changes can be detected.

I will be using C#.

Thanks,

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    The next best method (but one that involves reading every file completely, which I’d avoid when it can be helped) would be to compare file size and a hash (e.g. SHA-256) of the file contents. The probability that both collide is fairly slim, especially under normal circumstances.

    I’d use the GetFileInformationByHandle way on NTFS and fall back to hashing on FAT volumes.

    In Dropbox’ case I think though, that there is a service or process running in background observing file system changes. It’s the most reliable way, even if it ceases to work if you stop said service/process.

    • 0