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, 3.5, 3.0
.NET Framework Client Profile
Supported in: 4, 3.5 SP1
Windows 7, 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
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.