public void Activate()

{
  //cast ICatalogWindow to ArcGIS.Desktop.Framework.Contracts.DockPane
  var catalogWindow = Project.GetCatalogPane() as DockPane;
  //Activate it
  catalogWindow.Activate();
}

{
  // in order to find a dockpane you need to know its DAML id
  pane = FrameworkApplication.DockPaneManager.Find(dockPaneID);

  // determine visibility
  bool visible = pane.IsVisible;

  // activate it
  pane.Activate();

  // determine dockpane state
  DockPaneState state = pane.DockState;

  // pin it
  pane.Pin();

  // hide it
  pane.Hide();
}