When you try to use a feature that the Xbox version does not support, an InvalidOperation is thrown. When you catch that exception, you can be sure that a Xbox kinect is connected.
try
{
sensor.DepthStream.Range = DepthRange.Near;
sensor.SkeletonStream.EnableTrackingInNearRange = true;
}
catch (InvalidOperationException)
{
// Non Kinect for Windows devices do not support Near mode, so reset back to default mode.
sensor.DepthStream.Range = DepthRange.Default;
sensor.SkeletonStream.EnableTrackingInNearRange = false;
}