VirtualizingPanel.IsVirtualizingWhenGrouping Attached Property
Gets or sets a value that indicates whether this VirtualizingPanel virtualizes the items in its collection when it displays groups.
Assembly: PresentationFramework (in PresentationFramework.dll)
The standard layout system creates item containers and computes layout for each item associated with a list control. In this context, "virtualize" refers to a technique by which a subset of user interface (UI) elements are generated from a larger number of data items based on which items are visible on the screen. It is intensive, both in terms of memory and processor, to generate a large number of UI elements when only a few may be on the screen at a given time.