Silverlight ListBox: How to find out if user is currently dragging the scrollbar slider?

Scenario: I have a ListBox, containing a WrapPanel from the Silverlight Toolkit as ItemsPanel:

<ListBox x:Name="listBoxFaelle">
    <ListBox.ItemsPanel>
        <ItemsPanelTemplate>
        开发者_如何学Python    <toolkit:WrapPanel />
        </ItemsPanelTemplate>
    </ListBox.ItemsPanel>
    <ListBox.Template>
        <ControlTemplate>
            <Grid>
                <ScrollViewer>
                    <ItemsPresenter />
                </ScrollViewer>
            </Grid>
        </ControlTemplate>
    </ListBox.Template>
</ListBox>

This ListBox gets populated automatically with the results of a RIA service call every 60 seconds. While the application is waiting for the LoadOperation to complete, it displays the standard BusyIndicator that is part of the Silverlight Business Application template.

This works fine as long as the user is not dragging the scrollbar slider of the ListBox when the Timer Event fires.

Problem: If the user is dragging the scrollbar slider when the BusyIndicator is being displayed, the scrollbar doesn’t work anymore, afterwards. It looks like the mouse pointer remains captured to the slider even if the left mouse button is released. I assume this happens because the BusyIndicator temporarily takes away the focus from the slider while it is being dragged.

Question: Is there a way to find out if the scrollbar slider of the ListBox is currently being pushed?

As far as I know there is no status/property to find out if the slider is being pushed.

That said you could try to keep track of it yourself by handling MouseLeftButtonDown and Up events but you might have to consider other events as well depending on your scenario (mouse wheel?)

MouseLeftButtonUp Occurs when the left mouse button is released (or the tip of the stylus is removed from the tablet) while the mouse (or the stylus) is over a UIElement (or while a UIElement holds mouse capture). (Inherited from UIElement.)

It might also be possible to solve this the other way around by releasing the MouseCapture (if that is causing the problem) by using ReleaseMouseCapture

Again, it depends on what you want to happen from the user's point of view: skip the loading of the data (this is what I would prefer because I do not like the content to be changing when I am scrolling) or reset the listbox and scroll to the top (ugly in my opinion)