VB.NET. "The process cannot access the file because it is being used by another process"

Copper Contributor

I should add a list of files into a ZIP. Procedure code is like this

Sub CreateZip
    Dim FileList As New ArrayList   'List of File Paths to be added to the ZIP
    For Each path in FileList
            AddFileToZip(ZipFilePath, path.ToString)
        Catch (ex as New Exception)
        End Try
End Sub

And this is AddFileToZip

    Public Sub AddFileToZip(ByVal zipFilename As String, ByVal fileToAdd As String)
    Using zip As Package = System.IO.Packaging.Package.Open(zipFilename, FileMode.OpenOrCreate)
        Dim destFilename As String = ".\" & Path.GetFileName(fileToAdd)
        Dim uri As Uri = PackUriHelper.CreatePartUri(New Uri(destFilename, UriKind.Relative))
        If zip.PartExists(uri) Then
        End If
        Dim part As PackagePart = zip.CreatePart(uri, "", CompressionOption.Normal)
        Using fileStream As New FileStream(fileToAdd, FileMode.Open, FileAccess.Read)
            Using dest As Stream = part.GetStream()
                CopyStream(fileStream, dest)
            End Using
        End Using
    End Using
End Sub

At runtime, I get this error message

The process cannot access the file [ZipFilePath] because it is being used by another process

this error is raised randomly, maybe on adding small files into the Zip. If I place breakpoints and run procedure in debug mode, it works.

It seems clear that procedure thread is not synchronized with IO, so that my procedure loop continues even if IO is still adding processed file into Zip (ie VB.NET is faster than IO).

I also tried to place a Thread.Sleep(1000) before AddFileToZip, but this may be not enough to synchronize the two processes. Placing Thread.Sleep(2000) seems to make procedure work, but it may slow down dramaticly performances (I should pack more than 50 files into my Zip).

So, how can I force my loop to "wait" until IO Process has released ZIP file?

4 Replies

Hi @mr_anto,

Thanks for posting your issue here.

However this platform is used for how-to discussions and sharing best practices for building any app with .NET.Since your issue is a technical question, welcome to post it in Microsoft Q&A forum, the support team and communities on Microsoft Q&A will help you for any technical questions.
Besides, it will be appreciated if you can share it here once you post this technical question Microsoft Q&A.
Best Regards,
Lan Huang

sorry, i will redirect my question to microsoft Q&A. thanks
I tried to write my question in Q&A forum, but it was blocked by Azure Firewall: "WAF v2 has determined your request exceeded the normal web request and has blocked your request".
what's wrong?

@mr_anto Sorry if this is late, probably you already fixed it. 

Try move

    Using zip As Package = System.IO.Packaging.Package.Open(zipFilename, FileMode.OpenOrCreate)

outside of 


 this is because every time you add a file, you try to reopen the zip, which is not very useful.

Open it once, and then add all files to it.