public Row CurrentRow {get;}

//Return the page number that corresponds to the page name field for an index feature

Layout layout = LayoutView.Active.Layout;

//Perform on the worker thread
await QueuedTask.Run(() =>
{
  SpatialMapSeries SMS = layout.MapSeries as SpatialMapSeries;
  Row msRow = SMS.CurrentRow;
  System.Windows.MessageBox.Show(SMS.FindPageNumber(msRow.GetOriginalValue(msRow.FindField("NAME")).ToString()));
});