public MapView ActivatedMapView {get;}

//The active view must be a layout view.
var lv = LayoutView.Active;
if (lv == null)
  return;

var map_view = lv.ActivatedMapView;
if (map_view != null)
{
  //TODO - use activated map view
}
var map_frame = lv.ActivatedMapFrame;
if (map_frame != null)
{
  //TODO - use activated map frame
}