FocusManager.IsFocusScope Attached Property
Determines whether the element this property is attached to is a focus scope.
Assembly: PresentationCore (in PresentationCore.dll)
A focus scope is a container element that keeps track of the FocusManager.FocusedElement within its scope. By default, the Window class is a focus scope as are the Menu, ContextMenu, and ToolBar classes. An element which is a focus scope has set to true.
For more information on focus, keyboard focus, and logical focus, see the Input Overview.