public void Activate()

{
  var mapPanes = FrameworkApplication.Panes.OfType<IMapPane>();
  foreach (Pane p in mapPanes.Cast<Pane>())
  {
    if (p.Caption == paneID)
    {
      p.Activate();
      break;
    }
  }
}

{
  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();
    }
  }
}

{
  //Note: Needs QueuedTask to run
  Report reportToActivate = Project.Current.GetItems<ReportProjectItem>().FirstOrDefault().GetReport();
  var reportPane = FrameworkApplication.Panes.FindReportPanes(report).Last();
  if (reportPane == null)
    return;
  //Activate the pane
  (reportPane as ArcGIS.Desktop.Framework.Contracts.Pane).Activate();
  //Get the "ReportView" associated with the Report Pane.
  ReportView reportViewFromPane = reportPane.ReportView;
}

{
  //Activate an already open layout view.
  //A layout view may be open but it may not be active.

  //Find the pane that references the layout and activate it. 
  //Note - there can be multiple panes referencing the same layout.
  foreach (var pane in ProApp.Panes)
  {
    var layoutPane = pane as ILayoutPane;
    if (layoutPane == null)  //if not a layout view, continue to the next pane
      continue;
    if (layoutPane.LayoutView.Layout == layout) //activate the view
    {
      (layoutPane as Pane).Activate();
      return;
    }
  }
}