static bool _isScanningFinished;


/// <summary>
/// Asynchronously acquires images from TWAIN device.
/// </summary>
public static void AsynchronouslyAcquireImageFromTwainDevice()
{
    _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
        string deviceName = "KODAK Scanner: i5000";
        Vintasoft.Twain.Device device = deviceManager.Devices.Find(deviceName);
        if (device == null)
            throw new System.ApplicationException(string.Format("Device '{0}' is not found.", deviceName));

        // subscribe to device events
        SubscribeToDeviceEvents(device);

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

        // open the device
        device.Open();

        // specify that black-white images must be acquired
        device.PixelType = Vintasoft.Twain.PixelType.BW;
        // specify the threshold for acquired images
        device.Threshold = 128;
        // 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 acquisition is in progress.
/// </summary>
private static void device_ImageAcquiringProgress(object sender, Vintasoft.Twain.ImageAcquiringProgressEventArgs e)
{
    // update progress bar
}

/// <summary>
/// Image is acquired.
/// </summary>
private static void device_ImageAcquired(object sender, Vintasoft.Twain.ImageAcquiredEventArgs e)
{
    // add the acquired image to a TIFF file
    e.Image.Save(System.IO.Path.Combine(System.IO.Directory.GetCurrentDirectory(), "multipage.tif"));

    // dispose the acquired image
    e.Image.Dispose();
}

/// <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.ImageAcquiringProgress += new System.EventHandler<Vintasoft.Twain.ImageAcquiringProgressEventArgs>(device_ImageAcquiringProgress);
    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.ImageAcquiringProgress -= new System.EventHandler<Vintasoft.Twain.ImageAcquiringProgressEventArgs>(device_ImageAcquiringProgress);
    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>
''' Asynchronously acquires images from TWAIN device.
''' </summary>
Public Shared Sub AsynchronouslyAcquireImageFromTwainDevice()
        _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 deviceName As String = "KODAK Scanner: i5000"
                Dim device As Vintasoft.Twain.Device = deviceManager.Devices.Find(deviceName)
                If device Is Nothing Then
                        Throw New System.ApplicationException(String.Format("Device '{0}' is not found.", deviceName))
                End If

                ' subscribe to device events
                SubscribeToDeviceEvents(device)

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

                ' open the device
                device.Open()

                ' specify that black-white images must be acquired
                device.PixelType = Vintasoft.Twain.PixelType.BW
                ' specify the threshold for acquired images
                device.Threshold = 128
                ' 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 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 acquisition is in progress.
''' </summary>
Private Shared Sub device_ImageAcquiringProgress(sender As Object, e As Vintasoft.Twain.ImageAcquiringProgressEventArgs)
        ' update progress bar
End Sub

''' <summary>
''' Image is acquired.
''' </summary>
Private Shared Sub device_ImageAcquired(sender As Object, e As Vintasoft.Twain.ImageAcquiredEventArgs)
        ' add the acquired image to a TIFF file
        e.Image.Save(System.IO.Path.Combine(System.IO.Directory.GetCurrentDirectory(), "multipage.tif"))

        ' dispose the acquired image
        e.Image.Dispose()
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.ImageAcquiringProgress, New System.EventHandler(Of Vintasoft.Twain.ImageAcquiringProgressEventArgs)(AddressOf device_ImageAcquiringProgress)
        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.ImageAcquiringProgress, New System.EventHandler(Of Vintasoft.Twain.ImageAcquiringProgressEventArgs)(AddressOf device_ImageAcquiringProgress)
        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