Question

I’m creating a Windows application which use FileSystemWatcher. FileSystemWatcher watches some catalog for changes. And every time some file is added to this catalog FileSystemWatcher must add information about this file to an XML file. All works fine, but, when I add, for example, 100 files at same time (say that some application adds these files to the catalog) not every file’s information appears in this xml file.

I want to use Queue. And use it to add items to this collection. And use a timer. The timer will add information to the XML from this collection. Is it good idea?

Can anyone advise me what to do?

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So i think that i must create a Windows application and a Windows Service. WinApp will only add information to EventLog and Windows Service will read information EventLog and write it to XML. I think it will the best way to do it. I’m waiting for good advice

Answer 1

As Michael Stum writes in his answer, you could try increasing the buffer size (FileSystemWatcher.InternalBufferSize). Note however that you shouldn’t set this value to too high a value. Also, IMHO this is possibly only a temporary fix, see what happens when you add yet more files to your folder at the same time.

I have read about some other things you can attempt if increasing the buffer size doesn’t help:

• If you subscribe to the notification events of FileSystemWatcher, try to keep your event handler as short as possible; ie. make sure execution doesn’t stay there long. If you have to do a fair amount of work per file notification, you could try to start a separate thread and do the processing there; your event handler could then get back to the caller very quickly (and the file notification would get removed from the buffer/queue sooner).

• Don’t use any additional information provided by FileSystemWatcher apart from the basic notification that something has changed. Once you get any file change notification, wait a brief timespan until no more notifications arrive (ie. wait for the last notification out of 100 simultaneous file change notifications). Then list the contents of the directory manually and transfer the required information to your XML.

  This has one major drawback: Manually detecting whether, and which, files have been deleted, renamed, or created is not easy. Your program would have to keep the last directory listing against which the current listing can be compared to find out what’s changed.

  The advantage of this is that you can be fairly sure that no changes will be dropped due to some FileSystemWatcher buffer overflow.