decompress password protected zip files using shell32.dll

Hi.

I just had the same problem and found a workaround bymyself.
Maybe know you or anyone else could be still interested in.

So,what I did was basically:

Add a module with an API function to setthe found window in foreground:

Module mdlWinAPI
    Public Declare Ansi Function SetForegroundWindow Lib "user32.dll" _
     Alias "SetForegroundWindow" (ByVal hwnd As IntPtr) As Boolean
End Module

Then, I added a timer to my form, set to 1/4 second - just to look if there's a Window wich has that specific Caption ("Password Richiesta"). You must change that string to your language localization, i.e.: "Required Password".

The code inside the timer is:

Private Sub tmrCheck_Tick(ByVal sender As Object, ByVal e As EventArgs) _
 Handles tmrCheck.Tick
    ' Specify part of the window title you want.
    ' Get its window handle.
    Dim hwnd As IntPtr = Window_FindPartialTitle("Password Richiesta")
    If hwnd <> IntPtr.Zero Then
        tmrCheck.Stop()
        ' Set it foreground.
        SetForegroundWindow(hwnd)
        ' Insert the password.
        SendKeys.Send(Pwd_VideoPress)
        ' Send ENTER.
        SendKeys.Send("{ENTER}")
    End If
End Sub

Which uses the method:

Private Function Window_FindPartialTitle(ByVal partialTitle As String) _
 As IntPtr
    ' Find handle by partial window title
    For Each p As Process In Process.GetProcesses()
        If p.MainWindowTitle.IndexOf(partialTitle, 0, StringComparison.CurrentCultureIgnoreCase) > -1 Then
            Return p.MainWindowHandle
        End If
    Next
    Return IntPtr.Zero
End Function

The rest of my code doesn't do much: Shows the files inside the zip and Unzips them to a specified folder.

Hope that someone will find this workaround helpful.

You can unzip password protected zip files with ICSharpCode.SharpZipLib. It's free, and can be used in closed-source projects.