Selector.IsSelectionActive Attached Property
Gets a value that indicates whether the keyboard focus is within the value returned by a Selector.
Type: System.Booleantrue if the keyboard focus is within the Selector control; otherwise, false.
This is a rare case of a read-only attached property. You cannot set it in XAML; it exists so that you can check its value on selected items in code.
Supported in: 4.6, 4.5, 4, 3.5, 3.0
.NET Framework Client Profile
Supported in: 4, 3.5 SP1