Private VSTwain1 As New VintaSoftTwain()


''' <summary>
''' Scans images asynchronously.
''' </summary>
Private Sub ScanImages()
    VSTwain1.Device_Open()
    If VSTwain1.DeviceManager_ShowDefaultDeviceSelectionDialog() Then
        VSTwain1.Device_ShowUI = True

        Try
            ' get events supported by device
            Dim supportedDeviceEvents As Array = VSTwain1.Device_GetSupportedAsyncEvents()
            If (Not IsNothing(supportedDeviceEvents)) Then
                ' for each supported event
                For i As Integer = 0 To supportedDeviceEvents.Length - 1
                    ' if device can report when paper is jammed
                    If supportedDeviceEvents(i) = 13 Then
                        ' specify that device must report when paper is jammed
                        VSTwain1.Device_AsyncEvents = New Int32() {13}

                        ' subscribe to the device event
                        AddHandler VSTwain1.DeviceAsyncEvent, AddressOf VSTwain1_AsyncEvent

                        Exit For
                    End If
                Next
            End If
        Catch ex As Exception
            Console.WriteLine(ex.ToString())
        End Try

        ' subscribe to the device events
        AddHandler VSTwain1.DeviceImageAcquired, AddressOf VSTwain1_ImageAcquired
        AddHandler VSTwain1.DeviceScanCompleted, AddressOf VSTwain1_ScanCompleted
        AddHandler VSTwain1.DeviceScanFailed, AddressOf VSTwain1_ScanFailed
        AddHandler VSTwain1.DeviceScanCanceled, AddressOf VSTwain1_ScanCanceled

        ' acquire images asynchronously
        VSTwain1.Device_AcquireImage()
    End If
End Sub

Private Sub VSTwain1_AsyncEvent(deviceEvent As Integer, _
                                deviceName As String, _
                                batteryMinutes As Double, _
                                batteryPercentage As Short, _
                                powerSupply As Integer, _
                                resolutionX As Single, _
                                resolutionY As Single, _
                                flashUsed As Integer, _
                                automaticCapture As Double, _
                                timeBeforeFirstCapture As Double, _
                                timeBetweenCaptures As Double)
    Console.WriteLine("Paper is jammed.")
End Sub

Private Sub VSTwain1_ImageAcquired()
    ' get index of acquired image
    Dim imageIndex As Integer = VSTwain1.AcquiredImages_Count - 1

    ' save acquired image to TIFF file
    If Not VSTwain1.AcquiredImages_Save(0, "c:\test.tiff") Then
        Console.WriteLine(VSTwain1.errorString)
    End If
End Sub

Private Sub VSTwain1_ScanCompleted()
    Console.WriteLine("Scan is completed.")
End Sub

Private Sub VSTwain1_ScanFailed(errorString As String)
    Console.WriteLine(String.Format("Scan is failed: {0}.", errorString))
End Sub

Private Sub VSTwain1_ScanCanceled()
    Console.WriteLine("Scan is canceled.")
End Sub