FileSystemWatcher: Out Of Memory error

[Geespot]

Hi,

I have made a small application to monitor a directory. When I a new BMP file is added to that directory, my program converts it into a jpg file.

I have achieved this by using the FileSystemWatcher class.

Unfortunetely I recieved an 'Out Of Memory' error when a new bitmap file has been added to a folder.

The problem code is below

Private Sub FileSystemWatcher1_Created(ByVal sender As Object, ByVal e As System.IO.FileSystemEventArgs) Handles FileSystemWatcher1.Created
        ListBox1.Items.Add(e.FullPath)
 
        Dim img As Image
 
        img = Image.FromFile(e.FullPath)
 
        'blah blah blah, do something
 
        img.Dispose()
 
    End Sub

I recieve the error on this line

img = Image.FromFile(e.FullPath)

It never happens the first time this sub is called, its always on the second or greater.

Im out of ideas on what it could be, your help is much appreciated

Thanks

[scuzymoto]

I have had similar problems with the dispose method on images. Try adding a line right under the dispose line that says...

img.image = nothing

That cleared up some problems in my app that were related to memory. I wasn't running out of memory but it was complaining about errors related to memory. I don't remember the exact error.

[nemaroller]

Image.FromFile has an irky bug within its definition.


Use Image.FromStream instead

Private Sub FileSystemWatcher1_Created(ByVal sender As Object, ByVal e As System.IO.FileSystemEventArgs) Handles FileSystemWatcher1.Created
        ListBox1.Items.Add(e.FullPath)
 
        Dim img As Image
 
        Dim fs As New System.IO.FileStream(e.FullPath,Read)
         
        img = Image.FromStream(fs)
        fs.Close
 
        'blah blah blah, do something
 
        img.Dispose()
        img =Nothing
 
    End Sub

[Pirate]

Originally posted by scuzymoto
I have had similar problems with the dispose method on images. Try adding a line right under the dispose line that says...

img.image = nothing

That cleared up some problems in my app that were related to memory. I wasn't running out of memory but it was complaining about errors related to memory. I don't remember the exact error.

Dispose method has the effect of setting the object to null . So you don't have to set the object to null after disposal .

[Geespot]

Thanks,
Using a stream object did solve the Out Of Memory error, but has produced a new error.

my new code is

'-- A new image as been added, increment counter, this has no purpose!
        nThumbnailCount += 1
 
        '-- Get the filename of the new bitmap thats been added, without the BMP extension
        Dim sFilename As String = e.FullPath.Substring(0, e.FullPath.Length - 4)
 
        '-- Add a JPG extension to the string
        sFilename += ".jpg"
 
        '-- Copy the file, this is because you cant read a file when its in use
        System.IO.File.Copy(e.FullPath, "__null.bmp", True)
 
        '-- Open the BMP file in memory
        Dim oImg As Image
 
        '-- Read the image into a stream (this avoids the buggy .FromFile, and its faster too)
        Dim fs As New IO.FileStream("__null.bmp", IO.FileMode.Open, IO.FileAccess.Read)
        oImg = Image.FromStream(fs)
 
        '-- Immediately free up resources from stream, we have finished with it now
        fs.Close()
        fs = Nothing
 
        '-- Delete the copied file, dont need it now
        System.IO.File.Delete("__null.bmp")
 
        '-- Save the image into the JPG file
        'oImg.Save(sFilename, Imaging.ImageFormat.Jpeg)
 
        '-- Free up resources
        oImg.Dispose()

What Im doing is

• Copying the bitmap into a temporary file
• Opening the new copied file into a Stream
• Loading the stream into the Image object
• Freeing up the stream object
• Deleting the copied bitmap file
• Freeing up the Image object

To replicate the conditions of the program, I am simply pasting (in windows explorer) a bmp file into the folder that the FileSystemWatcher is monitoring, which calls the above code

After the second file that was pasted I get the following error

The process cannot access the file "__null.bmp" because it is being used by another process.

I have narrowed it down to this line

System.IO.File.Copy(e.FullPath, "__null.bmp", True)

Which I dont understand because that file shouldnt exist because my code deletes it.

I thought something like this would of been a walk in the park, guess I am over confident on such matters