Gets or sets a value specifying whether the Navigation Pane is expanded. This is a dependency property.
true if the Navigation Pane is expanded, otherwise false.
Use the IsExpanded property to expand and collapse the Navigation Pane programmatically. End-users can expand/collapse the Navigation Pane by clicking the Navigation Pane Expand Button, if it’s displayed, which is controlled by the NavigationPaneView.IsExpandButtonVisible property.
Note that you can also use the NavigationPaneCommands.ChangeNavPaneExpanded command to expand/collapse the Navigation Pane.