Invoke timeout after there has been no events in a given timeout

gistfile1.cs

            Observable.FromEvent<MapDragEventArgs>(Map, "MapPan")
                .Publish(mapPan_ =>
                {
                    mapPan_.Subscribe( _ =>
                        Observable.Timer(TimeSpan.FromMilliseconds(500))
                            .TakeUntil(mapPan_)
                            .Subscribe(__ => Debug.WriteLine("Timeout"))
                   );

                    return mapPan_;
                })
                .Subscribe(_ => Debug.WriteLine("MapPan"));