Batch Scanning consists of two parts: The call to acquire and the ImageAcquired event which is called when each page is scanned. The following example illustrates how this can be done:

Class Fields

// this goes in your class definition as a field for your application
private Acquisition _acquisition;
private Device _device;

Initialization

//This code would happen in your main constructor etc..

this._acquisition = new Acquisition();
if (this._acquisition.Devices.Default != null)
{
    this._device = this._acquisition.Devices.Default;
}
this._acquisition.ImageAcquired += new ImageAcquiredEventHandler(_acquisition_ImageAcquired);
this._acquisition.AcquireCanceled += new EventHandler(_acquisition_AcquireCanceled);
this._acquisition.AcquireFinished += new EventHandler(_acquisition_AcquireFinished);
this._acquisition.AsynchronousException += new AsynchronousExceptionEventHandler(_acquisition_AsynchronousException);

Please see the Acquisition Demo in our Legacy Demos KB article for a more complete implementation

Acquire

if (this._device == null)
{
    this._device = this._acquisition.Devices.Default;
}
this._device.Acquire();

Event handlers

private void _acquisition_ImageAcquired(object sender, Atalasoft.Twain.AcquireEventArgs e)
{
    // Perform for each scanned page
    if (e.Image != null)
    {
        AtalaImage currentImg = AtalaImage.FromBitmap(e.Image);
        // do whatever with currentImg
        currentImg.Dispose();
    }
}

private void _acquisition_AsynchronousException(object sender, AsynchronousExceptionEventArgs e)
{
    // Try to gracefully close the device so we don't end up "keeping our thumb on the scanner"
    if (this._device.State == TwainState.SourceOpen)
    {
        this._device.Close();
    }
    // in this simple example we're just blabbing the message.. 
    // production code would likely want to provide user friendly message and probably log the error 
    // message and StackTrace for use in troubleshooting
    MessageBox.Show("ERROR: " + e.Exception.Message);
}

private void _acquisition_AcquireFinished(object sender, EventArgs e)
{
    // there is no processing needed on finished but if you did need to take some action 
    // after a batch acquire finished, this is the place to do it
    if (this._device.State == TwainState.SourceOpen)
    {
        this._device.Close();
    }
}

private void _acquisition_AcquireCanceled(object sender, EventArgs e)
{
    // Again, we are just making sure we gracefully close the device so as not to cause 
    // errors where device is blocked because it's been left hanging
    if (this._device.State == TwainState.SourceOpen)
    {
        this._device.Close();
    }
}

Original Article:
Q10196 - HOWTO: Scan Images with DotTwain Acquire Method