static bool _isScanningFinished;

/// <summary>
/// Index of acquired image.
/// </summary>
static int _imageIndex;


/// <summary>
/// Uses File tranfer for saving TWAIN acquired images directly to a file on disk.
/// </summary>
public static void UseFileTransferForAcquiringImagesFromTwainDevice()
{
    _isScanningFinished = false;

    // create the device manager
    using (Vintasoft.Twain.DeviceManager deviceManager = new Vintasoft.Twain.DeviceManager())
    {
        deviceManager.IsTwain2Compatible = true;
        // open the device manager
        deviceManager.Open();

        // get the device
        Vintasoft.Twain.Device device = deviceManager.DefaultDevice;
        if (device == null)
            return;

        // subscribe to device events
        SubscribeToDeviceEvents(device);

        // disable device UI
        device.ShowUI = false;
        // set the File transfer mode
        device.TransferMode = Vintasoft.Twain.TransferMode.File;

        // open the device
        device.Open();

        // specify that grayscale images must be acquired
        device.PixelType = Vintasoft.Twain.PixelType.Gray;
        // set the inches as unit of measure
        device.UnitOfMeasure = Vintasoft.Twain.UnitOfMeasure.Inches;
        device.Resolution = new Vintasoft.Twain.Resolution(300f, 300f);

        // run asynchronous image acqusition
        device.Acquire();

        // wait while feeder will be stopped
        while (!_isScanningFinished)
        {
            System.Windows.Forms.Application.DoEvents();
        }

        // unsubscribe from device events
        UnsubscribeFromDeviceEvents(device);

        // close the device
        device.Close();
    }
}

/// <summary>
/// Image is acquiring.
/// </summary>
private static void Device_ImageAcquiring(object sender, Vintasoft.Twain.ImageAcquiringEventArgs e)
{
    string fileExtension = "bmp";
    switch (e.FileFormat)
    {
        case Vintasoft.Twain.TwainImageFileFormat.Tiff:
            fileExtension = "tif";
            break;

        case Vintasoft.Twain.TwainImageFileFormat.Jpeg:
            fileExtension = "jpg";
            break;
    }

    e.Filename = System.IO.Path.Combine(@"d:\images\", string.Format("page{0}.{1}", _imageIndex, fileExtension));
}

/// <summary>
/// Image is acquired.
/// </summary>
private static void device_ImageAcquired(object sender, Vintasoft.Twain.ImageAcquiredEventArgs e)
{
    System.Console.WriteLine(string.Format("Image is saved to a file '{0}'.", System.IO.Path.GetFileName(e.Filename)));
    _imageIndex++;
}

/// <summary>
/// Scan is completed.
/// </summary>
private static void device_ScanCompleted(object sender, System.EventArgs e)
{
    System.Console.WriteLine("Scan is completed.");
}

/// <summary>
/// Scan is canceled.
/// </summary>
private static void device_ScanCanceled(object sender, System.EventArgs e)
{
    System.Console.WriteLine("Scan is canceled.");
}

/// <summary>
/// Scan is failed.
/// </summary>
private static void device_ScanFailed(object sender, Vintasoft.Twain.ScanFailedEventArgs e)
{
    System.Console.WriteLine(string.Format("Scan is failed: {0}.", e.ErrorString));
}

/// <summary>
/// Scan is finished.
/// </summary>
private static void device_ScanFinished(object sender, System.EventArgs e)
{
    Vintasoft.Twain.Device device = (Vintasoft.Twain.Device)sender;

    // unsubscribe from device events
    UnsubscribeFromDeviceEvents(device);

    // if device is not closed
    if (device.State != Vintasoft.Twain.DeviceState.Closed)
        // close the device
        device.Close();

    System.Console.WriteLine("Scan is finished.");

    _isScanningFinished = true;
}

/// <summary>
/// Subscribes to the device events.
/// </summary>
private static void SubscribeToDeviceEvents(Vintasoft.Twain.Device device)
{
    device.ImageAcquiring += new System.EventHandler<Vintasoft.Twain.ImageAcquiringEventArgs>(Device_ImageAcquiring);
    device.ImageAcquired += new System.EventHandler<Vintasoft.Twain.ImageAcquiredEventArgs>(device_ImageAcquired);
    device.ScanCompleted += new System.EventHandler(device_ScanCompleted);
    device.ScanCanceled += new System.EventHandler(device_ScanCanceled);
    device.ScanFailed += new System.EventHandler<Vintasoft.Twain.ScanFailedEventArgs>(device_ScanFailed);
    device.ScanFinished += new System.EventHandler(device_ScanFinished);
}

/// <summary>
/// Unsubscribes from the device events.
/// </summary>
private static void UnsubscribeFromDeviceEvents(Vintasoft.Twain.Device device)
{
    device.ImageAcquiring -= new System.EventHandler<Vintasoft.Twain.ImageAcquiringEventArgs>(Device_ImageAcquiring);
    device.ImageAcquired -= new System.EventHandler<Vintasoft.Twain.ImageAcquiredEventArgs>(device_ImageAcquired);
    device.ScanCompleted -= new System.EventHandler(device_ScanCompleted);
    device.ScanCanceled -= new System.EventHandler(device_ScanCanceled);
    device.ScanFailed -= new System.EventHandler<Vintasoft.Twain.ScanFailedEventArgs>(device_ScanFailed);
    device.ScanFinished -= new System.EventHandler(device_ScanFinished);
}

Shared _isScanningFinished As Boolean

''' <summary>
''' Index of acquired image.
''' </summary>
Shared _imageIndex As Integer


''' <summary>
''' Uses File tranfer for saving TWAIN acquired images directly to a file on disk.
''' </summary>
Public Shared Sub UseFileTransferForAcquiringImagesFromTwainDevice()
    _isScanningFinished = False

    ' create the device manager
    Using deviceManager As New Vintasoft.Twain.DeviceManager()
        deviceManager.IsTwain2Compatible = True
        ' open the device manager
        deviceManager.Open()

        ' get the device
        Dim device As Vintasoft.Twain.Device = deviceManager.DefaultDevice
        If device Is Nothing Then
            Return
        End If

        ' subscribe to device events
        SubscribeToDeviceEvents(device)

        ' disable device UI
        device.ShowUI = False
        ' set the File transfer mode
        device.TransferMode = Vintasoft.Twain.TransferMode.File

        ' open the device
        device.Open()

        ' specify that grayscale images must be acquired
        device.PixelType = Vintasoft.Twain.PixelType.Gray
        ' set the inches as unit of measure
        device.UnitOfMeasure = Vintasoft.Twain.UnitOfMeasure.Inches
        device.Resolution = New Vintasoft.Twain.Resolution(300.0F, 300.0F)

        ' run asynchronous image acqusition
        device.Acquire()

        ' wait while feeder will be stopped
        While Not _isScanningFinished
            System.Windows.Forms.Application.DoEvents()
        End While

        ' unsubscribe from device events
        UnsubscribeFromDeviceEvents(device)

        ' close the device
        device.Close()
    End Using
End Sub

''' <summary>
''' Image is acquiring.
''' </summary>
Private Shared Sub Device_ImageAcquiring(sender As Object, e As Vintasoft.Twain.ImageAcquiringEventArgs)
    Dim fileExtension As String = "bmp"
    Select Case e.FileFormat
        Case Vintasoft.Twain.TwainImageFileFormat.Tiff
            fileExtension = "tif"
            Exit Select

        Case Vintasoft.Twain.TwainImageFileFormat.Jpeg
            fileExtension = "jpg"
            Exit Select
    End Select

    e.Filename = System.IO.Path.Combine("d:\images\", String.Format("page{0}.{1}", _imageIndex, fileExtension))
End Sub

''' <summary>
''' Image is acquired.
''' </summary>
Private Shared Sub device_ImageAcquired(sender As Object, e As Vintasoft.Twain.ImageAcquiredEventArgs)
    System.Console.WriteLine(String.Format("Image is saved to a file '{0}'.", System.IO.Path.GetFileName(e.Filename)))
    _imageIndex += 1
End Sub

''' <summary>
''' Scan is completed.
''' </summary>
Private Shared Sub device_ScanCompleted(sender As Object, e As System.EventArgs)
    System.Console.WriteLine("Scan is completed.")
End Sub

''' <summary>
''' Scan is canceled.
''' </summary>
Private Shared Sub device_ScanCanceled(sender As Object, e As System.EventArgs)
    System.Console.WriteLine("Scan is canceled.")
End Sub

''' <summary>
''' Scan is failed.
''' </summary>
Private Shared Sub device_ScanFailed(sender As Object, e As Vintasoft.Twain.ScanFailedEventArgs)
    System.Console.WriteLine(String.Format("Scan is failed: {0}.", e.ErrorString))
End Sub

''' <summary>
''' Scan is finished.
''' </summary>
Private Shared Sub device_ScanFinished(sender As Object, e As System.EventArgs)
    Dim device As Vintasoft.Twain.Device = DirectCast(sender, Vintasoft.Twain.Device)

    ' unsubscribe from device events
    UnsubscribeFromDeviceEvents(device)

    ' if device is not closed
    If device.State <> Vintasoft.Twain.DeviceState.Closed Then
        ' close the device
        device.Close()
    End If

    System.Console.WriteLine("Scan is finished.")

    _isScanningFinished = True
End Sub

''' <summary>
''' Subscribes to the device events.
''' </summary>
Private Shared Sub SubscribeToDeviceEvents(device As Vintasoft.Twain.Device)
    AddHandler device.ImageAcquiring, New System.EventHandler(Of Vintasoft.Twain.ImageAcquiringEventArgs)(AddressOf Device_ImageAcquiring)
    AddHandler device.ImageAcquired, New System.EventHandler(Of Vintasoft.Twain.ImageAcquiredEventArgs)(AddressOf device_ImageAcquired)
    AddHandler device.ScanCompleted, New System.EventHandler(AddressOf device_ScanCompleted)
    AddHandler device.ScanCanceled, New System.EventHandler(AddressOf device_ScanCanceled)
    AddHandler device.ScanFailed, New System.EventHandler(Of Vintasoft.Twain.ScanFailedEventArgs)(AddressOf device_ScanFailed)
    AddHandler device.ScanFinished, New System.EventHandler(AddressOf device_ScanFinished)
End Sub

''' <summary>
''' Unsubscribes from the device events.
''' </summary>
Private Shared Sub UnsubscribeFromDeviceEvents(device As Vintasoft.Twain.Device)
    RemoveHandler device.ImageAcquiring, New System.EventHandler(Of Vintasoft.Twain.ImageAcquiringEventArgs)(AddressOf Device_ImageAcquiring)
    RemoveHandler device.ImageAcquired, New System.EventHandler(Of Vintasoft.Twain.ImageAcquiredEventArgs)(AddressOf device_ImageAcquired)
    RemoveHandler device.ScanCompleted, New System.EventHandler(AddressOf device_ScanCompleted)
    RemoveHandler device.ScanCanceled, New System.EventHandler(AddressOf device_ScanCanceled)
    RemoveHandler device.ScanFailed, New System.EventHandler(Of Vintasoft.Twain.ScanFailedEventArgs)(AddressOf device_ScanFailed)
    RemoveHandler device.ScanFinished, New System.EventHandler(AddressOf device_ScanFinished)
End Sub