'Declaration Public Property MenuOrientation As Orientation
public Orientation MenuOrientation {get; set;}
For arranging the items, menu uses the panel supplied by ItemsPanel property. The default one is a StackPanel and it allows the items to be arranged vertical or horizontal. If you set another type panel, for example a Grid, then the MenuOrientation property will not be honored automatically. The Grid will take responsibility for arranging the items according its layout logic.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2