Gets or sets whether the sub-menu of the MenuItem is open.
This is effective only if the MenuItem is a submenu header (has child MenuItems).
This is a dependency property.
Namespace: Mindscape.SilverlightElementsAssembly: Mindscape.SilverlightElements (in Mindscape.SilverlightElements.dll) Version: 2.0.0.0 (2.0.0.0)