Handling multiple Change Events in FileSystemWatcher

Question

I have the following sub:

  Private Sub Watcher_Changed(ByVal sender As System.Object, ByVal e As FileSystemEventArgs)
        If Path.GetExtension(e.Name) = \".         


        

Answer 1

I created a service to upload files dumped to an FTP folder a couple years ago and here's some things I did that should help you get over your problem:

1. I tested all the NotifyFilters and chose the one that cut out duplicate notifications (using only NotifyFilters.Size gave me reliable notifications for every file created, and eliminated nearly all duplicate notifications)
2. In the Watcher_Changed event I ignored the file included in the event args and just processed all files currently in the folder; I try to add all files in the folder to a queue, and if they're already in the queue, I skip 3 below.
3. I spin off a new thread for every unique new file found; my thread tries to acquire a lock on the file, and if it can't that means some other process is still accessing it (it's still being uploaded, etc.) so my thread sleeps and tries again after a short interval.
4. When a file is completely processed, the last thing the thread does is move it to an archive folder, and then remove it from the queue, so it isn't accidentally processed again.

This seemed to work out for me and that service ran reliably uploading files for months until I left that job.