Gets or sets a value specifying the index of the group's selected item. This is a dependency property.
An integer value specifying the zero-based index of the selected item within the group. -1 if none of the group's items are curretly selected.
Read the SelectedItemIndex property value to obtain the index of the selected item within the group. The obtained value corresponds to the index of the NavBarItem object within the NavBarGroup.Items collection. Assign an index of an item to this property to select the item.
To learn more, see the Clicking and Selecting Items topic.