Group Headers and Footers

Each item that is added to the header or footer sections of a group configuration must be added as DataTemplates or GroupHeaderFooterItemTemplates, which must have a DataTemplate as an immediate child and whose VisibleWhenCollapsed property can be set to true (by default false) to keep the item visible when its containing group is collapsed. A group configuration's InitiallyExpanded property can also be set to provide an initial expansion state for all groups to which the configuration will be applied.

By default, group configurations contain a GroupHeaderControl in their header section that allow groups to be collapsed and expanded. In XAML, the content of a header or footer section can be cleared by setting the UseDefaultHeadersFooters property of a group configuration to false. If left to true, any items that are added to a header or footer section will be added after the default headers and footers.

Setting the UseDefaultHeadersFooters property to false will exclude the default header and footer items from all header and footer sections.
In code, the collections can be cleared by calling the Clear method.

Each template that is added to a header or footer section will create a container for itself in every individual group. A specific container can be identified through the use of a GroupHeaderFooterItem, which is created from the CollectionViewGroup in which the container is located and the template that was used to create it.