Bubbling scroll events from a ListView to its parent

Question

In my WPF application I have a ListView whose ScrollViewer.VerticalScrollBarVisibility is set to Disabled. It is contained within a

Answer 1

If you're coming here looking for a solution to bubble the event ONLY if the child is at the top and scrolling up or the bottom and scrolling down, here's a solution. I only tested this with DataGrid, but it should work with other controls as well.

public class ScrollParentWhenAtMax : Behavior
{
    protected override void OnAttached()
    {
        base.OnAttached();
        this.AssociatedObject.PreviewMouseWheel += PreviewMouseWheel;
    }

    protected override void OnDetaching()
    {
        this.AssociatedObject.PreviewMouseWheel -= PreviewMouseWheel;
        base.OnDetaching();
    }

    private void PreviewMouseWheel(object sender, MouseWheelEventArgs e)
    {
        var scrollViewer = GetVisualChild(this.AssociatedObject);
        var scrollPos = scrollViewer.ContentVerticalOffset;
        if ((scrollPos == scrollViewer.ScrollableHeight && e.Delta < 0)
            || (scrollPos == 0 && e.Delta > 0))
        {
            e.Handled = true;
            var e2 = new MouseWheelEventArgs(e.MouseDevice, e.Timestamp, e.Delta);
            e2.RoutedEvent = UIElement.MouseWheelEvent;
            AssociatedObject.RaiseEvent(e2);
        }
    }

    private static T GetVisualChild(DependencyObject parent) where T : Visual
    {
        T child = default(T);

        int numVisuals = VisualTreeHelper.GetChildrenCount(parent);
        for (int i = 0; i < numVisuals; i++)
        {
            Visual v = (Visual)VisualTreeHelper.GetChild(parent, i);
            child = v as T;
            if (child == null)
            {
                child = GetVisualChild(v);
            }
            if (child != null)
            {
                break;
            }
        }
        return child;
    }
}

To attach this behavior, add the following XMLNS and XAML to your element:

    xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"