How to force FileSystemWatcher to wait till the file downloaded?

Question

I am downloading a file and want to execute the install only after the download is complete. How do I accomplish this? Seems like FileSystemWatcher onCreate event would do this but this happens in a different thread, is there a simple way to force the waiting part to happen in the same thread.

Code I have so far

 FileSystemWatcher w = new FileSystemWatcher(@"C:/downloads");
 w.EnableRaisingEvents = true;
 w.Created += new FileSystemEventHandler(FileDownloaded);

 static void FileDownloaded(object source, FileSystemEventArgs e)
 {
    InstallMSI(e.FullPath);
 }

I looked at SynchronizingObject and WaitForChangedResult but didn't get a solid working sample.

downloading is being done in UI.. that code will make this question messy. I can only say that by the time this code is triggered, the download action has already started — satyajit, Mar 08 '11 at 20:29
possible duplicate of [FileSystemWatcher Work is Done?](http://stackoverflow.com/questions/4662893/filesystemwatcher-work-is-done) — Eugene Mayevski 'Callback, Mar 08 '11 at 20:36
Also check http://stackoverflow.com/questions/3822175/filesystem-watcher-and-large-files — Eugene Mayevski 'Callback, Mar 08 '11 at 20:37
File system watcher monitors changes in Directory or files in directory, it is not monitor when you finish changes in a file. Your downloading code must handle when downloading finishes. — ukhardy, Mar 08 '11 at 20:39

ukhardy · Answer 1 · 2011-03-08T20:51:39.877

16

Try:

FileInfo fInfo = new FileInfo(e.FullPath); 
while(IsFileLocked(fInfo)){
     Thread.Sleep(500);     
}
InstallMSI(e.FullPath);


static bool IsFileLocked(FileInfo file)
{
    FileStream stream = null;
    try {
        stream = file.Open(FileMode.Open, FileAccess.ReadWrite, FileShare.None);
    }
    catch (IOException) {
        return true;
    }
    finally {
        if (stream != null)
            stream.Close();
    }   
    return false;
}

edited Mar 08 '11 at 20:51

answered Mar 08 '11 at 20:44

ukhardy

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This is the most straight forward solution but I don't want to use more thread.sleeps in my code. So I am using the other approach – satyajit Mar 09 '11 at 06:20
I'm writing a console app and this worked perfectly. As I only have the one thread, I'm using this. +1. – JohnP Aug 29 '13 at 18:37
Perhaps add a check for if the file exists? – arachnode.net Jul 01 '15 at 05:24

Simen S · Answer 2 · 2011-03-08T20:57:41.783

5

If you insist on using FileSystemWatcher you would probably have to account for the fact that a file of some size isn't created (uploaded) in one single operation. The filesystem is likely to produce 1 created and x changed events before the file is ready for use.

You could catch the created events and create new (dedicated) threads (unless you already have an ongoing thread for that file) in which you loop and periodically try to open the file exclusively. If you succeed, the file is ready.

edited Mar 08 '11 at 20:57

answered Mar 08 '11 at 20:46

Simen S

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This is absolutely true. I've been using this for a simple sFTP transfer program, and even a 17k file copied from root to test directory produced 1 created and 4 changed events. – JohnP Aug 29 '13 at 18:38

score 2 · Answer 3 · answered Mar 08 '11 at 20:29

2

One technique would be to download to the temporary directory, and then move it into C:/downloads once it was complete.

answered Mar 08 '11 at 20:29

Chris Wenham

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How would I know if the download is complete, i.e when to trigger the move? – satyajit Mar 08 '11 at 20:34
Depends on how you're downloading it. What does the code look like? – Chris Wenham Mar 08 '11 at 20:40
2

Do x when download complete. Well that's the question! – ukhardy Mar 08 '11 at 20:50

score 2 · Answer 4 · answered Mar 08 '11 at 20:32

2

If you are using WebClient to download, you can use set the client's DownloadFileCompleted eventhandler.
If you do it this way you can also use client.DownloadFileAsync() to make it download asynchronously.

answered Mar 08 '11 at 20:32

Marcus

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How to force FileSystemWatcher to wait till the file downloaded?

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