Massive unzip application

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Introduction

This small application recursively extracts multiple zip files from a source folder and its subfolders to a destination folder. The source and destination folders can be the same. After the extraction, the user is asked to delete the zip files. Beyond its utility as an application, the code demonstrates the BackgroundWorker component, introduced in .NET framework v.2.

Background

For the unzip functionality, I used the SharpZipLib library freely available from the Sharpdevelop site. To understand the code, you have to read the documentation of the BackgroundWorker component. The BackgroundWorker component gives you the ability to execute time-consuming operations asynchronously ("in the background"), on a thread different from your application's main UI thread. Programming with the BackgroundWorker does not involve thread programming, you simple have to fill code in the appropriate event handlers. I used the design pattern of the component to keep the UI responsive while the files are unzipped in the background. The user also has the chance to cancel the operation.

The code

Functionality is implemented in the ZipUtils class file and specifically in the ExtractAllZips sub.

Sub ExtractAllZips()
    Dim d1, d2 As IO.DirectoryInfo
    d1 = New IO.DirectoryInfo(_sourceDir)
    d2 = New IO.DirectoryInfo(_targetDir)
    _iUnzip = 0
    extrAllZipsRecursive(d1, d2)
End Sub

Dim _iUnzip As Integer
Private Sub extrAllZipsRecursive(ByVal d1 As IO.DirectoryInfo, _
                                 ByVal d2 As IO.DirectoryInfo)
    Dim fi As IO.FileInfo, subd1, subd2 As IO.DirectoryInfo
    For Each fi In d1.GetFiles()
      If _worker.CancellationPending Then
        _dweArgs.Cancel = True
        Exit Sub
      End If
      If fi.Extension = ".zip" Then
        'increase decompress counter
        _iUnzip += 1
        Dim pctProg As Integer = (_iUnzip * 100) / ZipList.Count
        Worker.ReportProgress(pctProg, fi.FullName)
        ' extract zip or sleep for a while
        If Not _testMode Then
          ExtractZip(fi.FullName, d2.FullName)
        Else : System.Threading.Thread.Sleep(50)
        End If
      End If
    Next
    For Each subd1 In d1.GetDirectories()
      subd2 = d2.CreateSubdirectory(subd1.Name)
      extrAllZipsRecursive(subd1, subd2)
    Next
End Sub
  
Sub ExtractZip(ByVal zipFilename As String, ByVal targetDir As String)
    Try
      fz.ExtractZip(zipFilename, targetDir, FastZip.Overwrite.Always, Nothing, "", "")
    Catch ex As Exception
      Debug.WriteLine(ex.Message)
    End Try
End Sub

The ExtractAllZips sub is called from the handler of the BackgroundWorker's DoWork event, to be executed in the background.

Private Sub bkgWork1_DoWork(ByVal sender As Object, _
        ByVal e As System.ComponentModel.DoWorkEventArgs) Handles bkgWork1.DoWork
    ' Get the BackgroundWorker object that raised this event.
    Dim worker As BackgroundWorker = CType(sender, BackgroundWorker)
    ' get the zip utils that will do the work
    Dim zu As ZipUtils = CType(e.Argument, ZipUtils)
    zu.Worker = worker
    zu.DweArgs = e
    zu.FindAllZipsInDir()
    zu.ExtractAllZips()
End Sub

The process is initiated in the button's handler that calls the RunWorkerAsync method. Cancelling can be done by calling the CancelAsync method.

' unzip button, asynchronously
Private Sub btnUnzip_Click(ByVal sender As System.Object, _
            ByVal e As System.EventArgs) Handles btnUnzip.Click
    _zipUtils.SourceDir = TextBox1.Text
    _zipUtils.TargetDir = TextBox2.Text
    ' prepare interface
    adjustInterface(True)
    If _bWorking Then
      Me.bkgWork1.CancelAsync()
    Else
      Me.bkgWork1.RunWorkerAsync(_zipUtils)
      _bWorking = True
    End If
End Sub

Conclusion

I enjoyed creating this small program, I hope you'll find it useful!

History

• Version 1.0.