public interface IMapPane 

{
    ProApp.Panes.OfType<IMapPane>().OrderBy((mp) => mp.MapView.Map.URI ?? mp.MapView.Map.Name);
}

{
    //Gets the unique list of Maps from all the MapPanes.
    //Note: The list of maps retrieved from the MapPanes
    //maybe less than the total number of Maps in the project.
    //It depends on what maps the user has actually opened.
    var mapPanes = ProApp.Panes.OfType<IMapPane>()
                .GroupBy((mp) => mp.MapView.Map.URI).Select(grp => grp.FirstOrDefault());
    List<Map> uniqueMaps = new List<Map>();
    foreach (var pane in mapPanes)
        uniqueMaps.Add(pane.MapView.Map);
}

{
  string mapPaneCaption = "USNationalParks";
  IMapPane mapViewPane = FrameworkApplication.Panes.OfType<IMapPane>().FirstOrDefault((p) => p.Caption == mapPaneCaption);
  mapView = null;
  if (mapViewPane != null)
  {
    // activate the MapPane
    (mapViewPane as Pane).Activate();

    if (mapView != null)
    {
      // get the layers selected in the map's TOC
      var selectedLayers = mapView.GetSelectedLayers();
    }
  }
}