InputManager.PushMenuMode Method (PresentationSource)
Called by components to enter menu mode.
Assembly: PresentationCore (in PresentationCore.dll)
A component calls this method to enter the input manager’s menu mode. The menuSite gets privileged access to window messages. Calling this method causes the internal count of open menus to increment and sets the IsInMenuMode property to true, if this is the first menu to open.
Available since 4.0