Gets or sets whether the AppBar is visible.
true, if the AppBar is visible; otherwise, false. The default value is false.
By default, the app bar is hidden from view and appears when an end-user right clicks. The AppBar provides you with the IsOpen property to specify whether the app bar is visible. You can set this property in XAML to define the initial state of the app bar. You can also respond to end-user actions and show or hide the app bar by setting the AppBar.IsOpen property in code.
The IsOpen property cannot be set to false if the AppBar.HideMode property equals AlwaysVisible.