FileSystemWatcher.Created checks for completed files?

20 Apr 2006 8:18 AM

mathiasfritsch

Does FileSystemWatcher.Created event fires when the file is created,
or when writing the File is completed? In my App users upload files via
FTP and I want to start handling the files when they are completely
Uploaded.

Mathias

20 Apr 2006 1:32 PM

jimNOSPAMwooley

> Does FileSystemWatcher.Created event fires when the file is created,
> or when writing the File is completed? In my App users upload files
> via FTP and I want to start handling the files when they are
> completely Uploaded.

I have not found an ideal solution to this issue. Windows fires the event
multiple times as the file is being created. Check out the FileMon tool on
SysInternals.com to watch some of the IO that is happening behind the scenes.
The FileSystemWatcher is essentially a wrapper around the WIN32 API's that
handle the IO messages.

In my case, I have used the following scheme to handle the case of a file
that is being uploaded to wait until the upload has completed before processing.

Public Sub ProcessFile()

Sleep(1000) 'Wait a bit before proceeding to let them finish
TRY
   'Move the file to a processing directory
Catch ex as System.IO.IOException
   'File not yet availabl, wait and try again
   ProcessFile()
   Exit Sub
End Try

'Proceed with processing the file in the new temp location.

Jim Wooley
http://devauthority.com/blogs/jwooley

21 Apr 2006 8:53 AM

mathiasfritsch

Jim,
good point: I checked with FileMon and see that I realy have an issue
here.

I will use File.OpenWrite to check, if the the file is complete.
As you said, not an ideal solution, but its should work.

regards

Mathias

21 Apr 2006 10:43 AM

Damien

jimNOSPAMwooley@hotmail.com wrote:
Show quote

> > Does FileSystemWatcher.Created event fires when the file is created,
> > or when writing the File is completed? In my App users upload files
> > via FTP and I want to start handling the files when they are
> > completely Uploaded.
>
> I have not found an ideal solution to this issue. Windows fires the event
> multiple times as the file is being created. Check out the FileMon tool on
> SysInternals.com to watch some of the IO that is happening behind the scenes.
> The FileSystemWatcher is essentially a wrapper around the WIN32 API's that
> handle the IO messages.
>
> In my case, I have used the following scheme to handle the case of a file
> that is being uploaded to wait until the upload has completed before processing.
>
> Public Sub ProcessFile()
>
> Sleep(1000) 'Wait a bit before proceeding to let them finish
> TRY
>    'Move the file to a processing directory
> Catch ex as System.IO.IOException
>    'File not yet availabl, wait and try again
>    ProcessFile()
>    Exit Sub
> End Try
>
> 'Proceed with processing the file in the new temp location.

If the file writing took a further minute from the point at which you
first call ProcessFile, would you not end up with 60 calls to
ProcessFile with 60 exceptions sitting on the stack?

Wouldn't the following be better:

Public Sub ProcessFile()
Dim bAvailable as Boolean = False
While Not bAvailable
    Try
      'Move the file to new location
      bAvailable = True
    Catch Ex as System.IO.IOException
      'Optionally, count how many times we reach here
      'and if it's a large number, call Throw, since it doesn't
      'seem like we'll ever succeed
      Sleep(1000)
    End Try
End While

'Proceed with processing
End Sub

I'm trying to work out if there's a way to tell whether we can access
the file which doesn't invoke exception handling. Not sure.

Damien

24 Apr 2006 7:23 AM

mathiasfritsch

Damien,
you are right. There are 60 Exceptions in this case.
When I looked at FileMon I saw that the file size is displayed at the
very beginning of uploading.
I thing it is possible to compare the filesize as given in the header
of the file and the number of bytes already transfered.

But this is just an idea, I didnt check any further.

regards Mathias