How to determine if a Directory/Folder has been changed

Question

I have a folder with the following structure

Parent/
    Child1/
        GrandChild1/
             File1.txt

I need to query Parent folder and find out if Child1 has changed.

Changed = A new file was add/update/deleted.

The Child1 folder DateModified is not updated. Only the GrandChild1 date modified was updated when changes occurs. I am trying to avoid going to the file level to determine if the rootparent has changed. since there will be many folders and sub folder. I just need to know if Child1 has changed.

I do not want to use FileSystemWatcher, since I am running this as a scheduled job and not watching it LIVE.

Answer 1

User FileSystemWatcher. Remember to enable raising events since it is a common mistake (watchfolder.EnableRaisingEvents = true;).

The FileSystemWatcher may prove not to be optimal from a performance perspective. If that is an issue for you, you might implement a CRC check with a Timer to check for changes of the files and folders you are interested in.

Essentially, what I would do is to generate a CRC32 hash for the entire folder I am watching (and save it away into variable A) and when I decide it is time to check for changes, you simply calculate a new CRC32 hash for the same folder (into variable B). You then compare A with B and if they don´t match, something has changed. Really not that difficult.

Reference:

• http://www.codeproject.com/Articles/26528/C-Application-to-Watch-a-File-or-Directory-using-F
• http://social.msdn.microsoft.com/Forums/zh/netfxbcl/thread/b7612249-eb32-4005-9d6b-7f291c218326
• http://damieng.com/blog/2006/08/08/calculating_crc32_in_c_and_net
• http://marknelson.us/1992/05/01/file-verification-using-crc-2/

Answer 2

Have you tried the file system watcher? You can monitor local drives for changes from a given path, and then if necessary, ignore or process the fact they changed.

Answer 3

You can use the FileSystemWatcher Class for this.

Alternatively, if you would rather schedule a Task to run, Weekly, for example, you might want to have a look at: http://taskscheduler.codeplex.com/ and http://www.emoreau.com/Entries/Articles/2004/08/Interfacing-the-Windows-Task-Scheduler.aspx

And here's a link to the Windows Task Schedular API