public partial class WpfImageViewer_ExternalScrollBars : System.Windows.Window
{

    #region Constructors

    public WpfImageViewer_ExternalScrollBars()
    {
        InitializeComponent();
        // ...
        imageViewer.ImageLoaded += new System.EventHandler<Vintasoft.Imaging.ImageLoadedEventArgs>(imageViewer_ImageLoaded);
        imageViewer.ZoomChanged += new System.EventHandler<Vintasoft.Imaging.UI.ZoomChangedEventArgs>(imageViewer_ZoomChanged);
        imageViewer.SizeChanged += new System.Windows.SizeChangedEventHandler(imageViewer_SizeChanged);
        horizontalScrollBar.ValueChanged +=
            new System.Windows.RoutedPropertyChangedEventHandler<double>(ScrollBar_ValueChanged);
        verticalScrollBar.ValueChanged +=
            new System.Windows.RoutedPropertyChangedEventHandler<double>(ScrollBar_ValueChanged);

        imageViewer.AutoScroll = false;
        // ...
    }

    #endregion



    #region Methods

    /// <summary>
    /// Image is loaded in image viewer.
    /// </summary>
    private void imageViewer_ImageLoaded(object sender, Vintasoft.Imaging.ImageLoadedEventArgs e)
    {
        SetScrollBarsParams();
    }

    /// <summary>
    /// Image viewer size is changed.
    /// </summary>
    private void imageViewer_SizeChanged(object sender, System.Windows.SizeChangedEventArgs e)
    {
        SetScrollBarsParams();
    }

    /// <summary>
    /// Image viewer zoom is changed.
    /// </summary>
    private void imageViewer_ZoomChanged(object sender, Vintasoft.Imaging.UI.ZoomChangedEventArgs e)
    {
        SetScrollBarsParams();
    }

    /// <summary>
    /// Sets parameters of scroll bars.
    /// </summary>
    private void SetScrollBarsParams()
    {
        // initialize horizontal scroll bar
        horizontalScrollBar.Minimum = 0;
        horizontalScrollBar.Maximum = imageViewer.ViewerState.AutoScrollSize.Width;
        horizontalScrollBar.Track.ViewportSize = imageViewer.ActualWidth;

        // initialize vertical scroll bar
        verticalScrollBar.Minimum = 0;
        verticalScrollBar.Maximum = imageViewer.ViewerState.AutoScrollSize.Height;
        verticalScrollBar.Track.ViewportSize = imageViewer.ActualHeight;
    }

    /// <summary>
    /// Scroolbar is changed.
    /// </summary>
    private void ScrollBar_ValueChanged(object sender, System.Windows.RoutedPropertyChangedEventArgs<double> e)
    {
        System.Windows.Point currentPosition =
            new System.Windows.Point(horizontalScrollBar.Value, verticalScrollBar.Value);
        imageViewer.ViewerState.AutoScrollPosition = currentPosition;
    }

    #endregion

}

Public Partial Class WpfImageViewer_ExternalScrollBars
    Inherits System.Windows.Window

    #Region "Constructors"

    Public Sub New()
        InitializeComponent()
        ' ...
        AddHandler imageViewer.ImageLoaded, New System.EventHandler(Of Vintasoft.Imaging.ImageLoadedEventArgs)(AddressOf imageViewer_ImageLoaded)
        AddHandler imageViewer.ZoomChanged, New System.EventHandler(Of Vintasoft.Imaging.UI.ZoomChangedEventArgs)(AddressOf imageViewer_ZoomChanged)
        AddHandler imageViewer.SizeChanged, New System.Windows.SizeChangedEventHandler(AddressOf imageViewer_SizeChanged)
        AddHandler horizontalScrollBar.ValueChanged, New System.Windows.RoutedPropertyChangedEventHandler(Of Double)(AddressOf ScrollBar_ValueChanged)
        AddHandler verticalScrollBar.ValueChanged, New System.Windows.RoutedPropertyChangedEventHandler(Of Double)(AddressOf ScrollBar_ValueChanged)

            ' ...
        imageViewer.AutoScroll = False
    End Sub

    #End Region



    #Region "Methods"

    ''' <summary>
    ''' Image is loaded in image viewer.
    ''' </summary>
    Private Sub imageViewer_ImageLoaded(sender As Object, e As Vintasoft.Imaging.ImageLoadedEventArgs)
        SetScrollBarsParams()
    End Sub

    ''' <summary>
    ''' Image viewer size is changed.
    ''' </summary>
    Private Sub imageViewer_SizeChanged(sender As Object, e As System.Windows.SizeChangedEventArgs)
        SetScrollBarsParams()
    End Sub

    ''' <summary>
    ''' Image viewer zoom is changed.
    ''' </summary>
    Private Sub imageViewer_ZoomChanged(sender As Object, e As Vintasoft.Imaging.UI.ZoomChangedEventArgs)
        SetScrollBarsParams()
    End Sub

    ''' <summary>
    ''' Sets parameters of scroll bars.
    ''' </summary>
    Private Sub SetScrollBarsParams()
        ' initialize horizontal scroll bar
        horizontalScrollBar.Minimum = 0
        horizontalScrollBar.Maximum = imageViewer.ViewerState.AutoScrollSize.Width
        horizontalScrollBar.Track.ViewportSize = imageViewer.ActualWidth

        ' initialize vertical scroll bar
        verticalScrollBar.Minimum = 0
        verticalScrollBar.Maximum = imageViewer.ViewerState.AutoScrollSize.Height
        verticalScrollBar.Track.ViewportSize = imageViewer.ActualHeight
    End Sub

    ''' <summary>
    ''' Scroolbar is changed.
    ''' </summary>
    Private Sub ScrollBar_ValueChanged(sender As Object, e As System.Windows.RoutedPropertyChangedEventArgs(Of Double))
        Dim currentPosition As New System.Windows.Point(horizontalScrollBar.Value, verticalScrollBar.Value)
        imageViewer.ViewerState.AutoScrollPosition = currentPosition
    End Sub

    #End Region

End Class