gistfile1.cs

public class ListViewOffset
{
    public double GetValue(ListBox listBox)
    {
        // Get parts
        var scrollViewer = listBox.FindElement<ScrollViewer>();
        var scrollBar = scrollViewer.FindElement<ScrollBar>();
        return scrollBar.Value;
    }
}

public static class VisualTreeHelperExtension
{
    public static T FindElement<T>(this DependencyObject rootElement)
        where T : DependencyObject
    {
        var q = new Queue<DependencyObject>();
        q.Enqueue(rootElement);
        while (q.Count != 0)
        {
            var e = q.Dequeue();
            if (e is T) return e as T;
            var c = VisualTreeHelper.GetChildrenCount(e);
            for (var i = 0; i < c; ++i)
            {
                q.Enqueue(VisualTreeHelper.GetChild(e, i));
            }
        }
        return null;
    }

    public static Rect GetBoundingRectWithMargin(this FrameworkElement element, FrameworkElement relativeTo)
    {
        var transform = element.TransformToVisual(relativeTo);
        var r = new Rect(0, 0, element.ActualWidth, element.ActualHeight);
        r = transform.TransformBounds(r);
        var m = element.Margin;
        return new Rect(new Point(r.Left - m.Left, r.Top - m.Top), new Point(r.Right + m.Right, r.Bottom + m.Bottom));
    }
}