public class LayoutClosingEvent : ArcGIS.Core.Events.CompositePresentationEvent<LayoutClosingEventArgs> 

//Report the event args when a layout is closing.

ArcGIS.Desktop.Layouts.Events.LayoutClosingEvent.Subscribe((args) =>
{
  System.Windows.MessageBox.Show("LayoutClosingEvent:" +
  Environment.NewLine +
  "   arg Layout: " + args.Layout.Name +
  Environment.NewLine +
  "   arg LayoutPane: " + args.LayoutPane.Caption);
});