namespace TwainExamples_CSharp
{
    public partial class How_to_detect_the_end_of_batch_job : System.Windows.Forms.Form
    {

        /// <summary>
        /// TWAIN device manager.
        /// </summary>
        Vintasoft.Twain.DeviceManager _deviceManager;

        /// <summary>
        /// Job counter.
        /// </summary>
        int _jobCounter = -1; 



        public How_to_detect_the_end_of_batch_job()
        {
            InitializeComponent();

            // create and open device manager
            _deviceManager = new Vintasoft.Twain.DeviceManager(this);
            _deviceManager.Open();
        }



        /// <summary>
        /// Acquire images asynchronously.
        /// </summary>
        public void AcquireImagesAsynchronously()
        {
            try
            {
                // get reference to the default device
                Vintasoft.Twain.Device device = _deviceManager.DefaultDevice;

                // subscribe to the device events
                device.ImageAcquired += new System.EventHandler<Vintasoft.Twain.ImageAcquiredEventArgs>(device_ImageAcquired);
                device.ScanCanceled += new System.EventHandler(device_ScanCanceled);
                device.ScanFailed += new System.EventHandler<Vintasoft.Twain.ScanFailedEventArgs>(device_ScanFailed);
                device.ScanFinished += new System.EventHandler(device_ScanFinished);

                // set scanning settings
                device.TransferMode = Vintasoft.Twain.TransferMode.Memory;
                device.ShowUI = true;

                // open the device
                device.Open();
                // specify that job separator must be searched and scanned
                device.JobControl = Vintasoft.Twain.JobControl.DetectAndIncludeJobSeparatorAndContinueScanning;
                // increment job count
                _jobCounter = _jobCounter + 1; 

                // acquire images asynchronously
                device.Acquire();
            }
            catch (Vintasoft.Twain.TwainException ex)
            {
                System.Windows.Forms.MessageBox.Show(ex.Message);
            }
        }

        /// <summary>
        /// Image is acquired.
        /// </summary>
        private void device_ImageAcquired(object sender, Vintasoft.Twain.ImageAcquiredEventArgs e)
        {
            Vintasoft.Twain.Device device = (Vintasoft.Twain.Device)sender;
            // if job separator is detected
            if (device.EndOfJob)
                // increment job count and do not save the job separator image
                _jobCounter = _jobCounter + 1;
            // if job separator is NOT detected
            else
                // add image to the multipage TIFF file for current job
                e.Image.Save(string.Format(@"d:\job{0}.tif", _jobCounter));

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

        /// <summary>
        /// Scan is canceled.
        /// </summary>
        private void device_ScanCanceled(object sender, System.EventArgs e)
        {
            System.Windows.Forms.MessageBox.Show("Scan is canceled.");
        }

        /// <summary>
        /// Scan is failed.
        /// </summary>
        private void device_ScanFailed(object sender, Vintasoft.Twain.ScanFailedEventArgs e)
        {
            System.Windows.Forms.MessageBox.Show("Scan is failed: " + e.ErrorString);
        }

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

            // unsubscribe from device events
            device.ImageAcquired -= new System.EventHandler<Vintasoft.Twain.ImageAcquiredEventArgs>(device_ImageAcquired);
            device.ScanCanceled -= new System.EventHandler(device_ScanCanceled);
            device.ScanFailed -= new System.EventHandler<Vintasoft.Twain.ScanFailedEventArgs>(device_ScanFailed);
            device.ScanFinished -= new System.EventHandler(device_ScanFinished);

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

            System.Windows.Forms.MessageBox.Show("Scan is finished.");
        }

    }
}

Partial Public Class How_to_detect_the_end_of_batch_job
    Inherits Form

    ''' <summary>
    ''' TWAIN device manager.
    ''' </summary>
    ''' <remarks></remarks>
    Private _deviceManager As Vintasoft.Twain.DeviceManager

    ''' <summary>
    ''' Job counter.
    ''' </summary>
    ''' <remarks></remarks>
    Private _jobCounter As Integer = -1



    Public Sub New()
        InitializeComponent()

        ' create and open device manager
        _deviceManager = New Vintasoft.Twain.DeviceManager(Me)
        _deviceManager.Open()
    End Sub



    ''' <summary>
    ''' Acquires images asynchronously.
    ''' </summary>
    Public Sub AcquireImagesAsynchronously()
        Try
            ' get reference to the default device
            Dim device1 As Vintasoft.Twain.Device = _deviceManager.DefaultDevice

            ' subscribe to the device events
            AddHandler device1.ImageAcquired, New EventHandler(Of Vintasoft.Twain.ImageAcquiredEventArgs)(AddressOf device_ImageAcquired)
            AddHandler device1.ScanCanceled, New EventHandler(AddressOf device_ScanCanceled)
            AddHandler device1.ScanFailed, New EventHandler(Of Vintasoft.Twain.ScanFailedEventArgs)(AddressOf device_ScanFailed)
            AddHandler device1.ScanFinished, New EventHandler(AddressOf device_ScanFinished)

            ' set scanning settings
            device1.TransferMode = Vintasoft.Twain.TransferMode.Memory
            device1.ShowUI = True

            ' open the device
            device1.Open()
            ' specify that job separator must be searched and scanned
            device1.JobControl = Vintasoft.Twain.JobControl.DetectAndIncludeJobSeparatorAndContinueScanning
            ' increment job count
            _jobCounter = _jobCounter + 1

            ' acquire images asynchronously
            device1.Acquire()
        Catch ex As Vintasoft.Twain.TwainException
            MessageBox.Show(ex.Message)
        End Try
    End Sub

    ''' <summary>
    ''' Image is acquired.
    ''' </summary>
    Private Sub device_ImageAcquired(ByVal sender As Object, ByVal e As Vintasoft.Twain.ImageAcquiredEventArgs)
        Dim device As Vintasoft.Twain.Device = DirectCast(sender, Vintasoft.Twain.Device)
        ' if job separator is detected
        If device.EndOfJob Then
            ' increment job count and do not save the job separator image
            _jobCounter = _jobCounter + 1
        Else
            ' if job separator is NOT detected
            ' add image to the multipage TIFF file for current job
            e.Image.Save(String.Format("d:\job{0}.tif", _jobCounter))
        End If

        ' dispose the acquired image
        e.Image.Dispose()
    End Sub

    ''' <summary>
    ''' Scan is canceled.
    ''' </summary>
    Private Sub device_ScanCanceled(ByVal sender As Object, ByVal e As EventArgs)
        MessageBox.Show("Scan is canceled.")
    End Sub

    ''' <summary>
    ''' Scan is failed.
    ''' </summary>
    Private Sub device_ScanFailed(ByVal sender As Object, ByVal e As Vintasoft.Twain.ScanFailedEventArgs)
        MessageBox.Show("Scan is failed: " + Convert.ToString(e.ErrorString))
    End Sub

    ''' <summary>
    ''' Scan is finished.
    ''' </summary>
    Private Sub device_ScanFinished(ByVal sender As Object, ByVal e As EventArgs)
        Dim device1 As Vintasoft.Twain.Device = DirectCast(sender, Vintasoft.Twain.Device)

        ' unsubscribe from device events
        RemoveHandler device1.ImageAcquired, New EventHandler(Of Vintasoft.Twain.ImageAcquiredEventArgs)(AddressOf device_ImageAcquired)
        RemoveHandler device1.ScanCanceled, New EventHandler(AddressOf device_ScanCanceled)
        RemoveHandler device1.ScanFailed, New EventHandler(Of Vintasoft.Twain.ScanFailedEventArgs)(AddressOf device_ScanFailed)
        RemoveHandler device1.ScanFinished, New EventHandler(AddressOf device_ScanFinished)

        ' if device is not closed
        If device1.State <> Vintasoft.Twain.DeviceState.Closed Then
            ' close the device
            device1.Close()
        End If

        MessageBox.Show("Scan is finished.")
    End Sub

End Class