Scrolls content upward by one page.
Assembly: PresentationFramework (in PresentationFramework.dll)
You can override in a derived class to change how the stack panel responds to the page up action.
If you require physical scrolling instead of logical scrolling, wrap the VirtualizingStackPanel in a ScrollViewer and set its CanContentScroll property to false. In this case, the ScrollViewer provides scrolling, and virtualization is disabled.