gistfile1.cs

public static class WidgetExtensions
{
   private static Thread _uiThread;
		
   /// <summary>
   /// Determines whether we need to invoke to get onto the UI thread
   /// </summary>
   public static bool InvokeRequired(this Gtk.Widget widget)
   {
      if(_uiThread == null)
      {				
         Application.Invoke((_,__) =>
         {
            _uiThread = Thread.CurrentThread;
         });
         return true;
      }
      if(Thread.CurrentThread == _uiThread)
      {
         return false;
      }
      return true;
   }
		
   /// <summary>
   /// Runs the action on the UI thread,
   /// Optimized to only invoke if we are not already on the UI thread.
   /// </summary>
   public static void Invoke(this Gtk.Widget widget, System.Action action)
   {
      if(widget.InvokeRequired())
      {
         Application.Invoke((_,__) =>
         {
            action();
         });
         return;
      }
      action();
   }
}