FileSystemWatcher.WaitForChanged surprising (wrong?) behaviour

I'm trying to use the System.IO.FileSystemWatcher class in code like...

using (FileSystemWatcher changeMonitor = new FileSystemWatcher("."))
{
for (; ; )
{
WaitForChangedResult c = changeMonitor.WaitForChanged(
WatcherChangeTypes.Created, 60 * 1000);

Console.WriteLine ("Creation");
}
}

and the code works as expected unless a file change /other/ than a
creation occurs in the folder, at which point the WaitForChanged call no
longer returns even after another creation.

So, in an empty folder

echo >a.txt ("Creation" is printed)
echo >b.txt ("Creation" is printed)
dele b.txt (nothing happens, as expected)
echo >c.txt (** nothing happens ... why? **)

Is this the intended behaviour? It seems rather surprising!

I note that if I change the code to pass WatcherChangeTypes.All, then
the code works as expected, but I get notification of changes I'm not
interested in.

--
Cheers,
John

Dave
Tue Nov 21 16:17:43 CST 2006

Hi John,

I was able to repro that behavior and it seems like a bug to me. You should
think about notifying Microsoft :)

Here's a work-around for you in the mean-time:

// 2.0 framework code:

using (FileSystemWatcher changeMonitor = new FileSystemWatcher("."))
{
System.Threading.EventWaitHandle wait =
new System.Threading.EventWaitHandle(false,
System.Threading.EventResetMode.AutoReset);

string createdFile = null;

changeMonitor.EnableRaisingEvents = true;
changeMonitor.Created +=
delegate(object sender, FileSystemEventArgs e)
{
createdFile = e.FullPath;
wait.Set();
};

while (true) // personal preference ;)
{
if (wait.WaitOne(60 * 1000, false))
{
Console.WriteLine(createdFile);
}
}
}

--
Dave Sexton

"John Aldridge" <no.spam@jjdash.demon.co.uk> wrote in message
news:MPG.1fcd1935d72afbf59896ae@news.demon.co.uk...
> I'm trying to use the System.IO.FileSystemWatcher class in code like...
>
> using (FileSystemWatcher changeMonitor = new FileSystemWatcher("."))
> {
> for (; ; )
> {
> WaitForChangedResult c = changeMonitor.WaitForChanged(
> WatcherChangeTypes.Created, 60 * 1000);
>
> Console.WriteLine ("Creation");
> }
> }
>
> and the code works as expected unless a file change /other/ than a
> creation occurs in the folder, at which point the WaitForChanged call no
> longer returns even after another creation.
>
> So, in an empty folder
>
> echo >a.txt ("Creation" is printed)
> echo >b.txt ("Creation" is printed)
> dele b.txt (nothing happens, as expected)
> echo >c.txt (** nothing happens ... why? **)
>
> Is this the intended behaviour? It seems rather surprising!
>
> I note that if I change the code to pass WatcherChangeTypes.All, then
> the code works as expected, but I get notification of changes I'm not
> interested in.
>
> --
> Cheers,
> John

John
Thu Nov 23 19:07:45 CST 2006

In article <uVjo$rbDHHA.1016@TK2MSFTNGP02.phx.gbl>, dave@jwa
[remove.this]online.com says...
> Hi John,
>
> I was able to repro that behavior and it seems like a bug to me. You should
> think about notifying Microsoft :)
>
> Here's a work-around for you in the mean-time:

(snip)

Thank you very much!

I've reported the problem
<https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?
FeedbackID=240502>

--
Cheers,
John