public interface ILayoutPane 

{
  //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;
    }
  }
}