var mouseMoveEvent = Observable.FromEvent<MouseEventArgs>( this, "MouseMove" );
            var mouseLeftButtonDown = Observable.FromEvent<MouseButtonEventArgs>( this, "MouseLeftButtonDown" );
            var mouseLeftButtonUp = Observable.FromEvent<MouseButtonEventArgs>( this, "MouseLeftButtonUp" );
            
            var clickingEvents = from pos in mouseLeftButtonDown
                                     .Let(mm => mm.Zip(mm.Skip(1), (prev, cur) =>
                                        new
                                        {
                                            IsClick = true,
                                            X2 = cur.EventArgs.GetPosition( this ).X,
                                            X1 = prev.EventArgs.GetPosition( this ).X,
                                            Y2 = cur.EventArgs.GetPosition( this ).Y,
                                            Y1 = prev.EventArgs.GetPosition( this ).Y
                                        } ) ).Repeat()
                                 select pos;

            
            var draggingEvents = from pos in mouseMoveEvent.SkipUntil( mouseLeftButtonDown )
                                     .SkipUntil(mouseLeftButtonDown)
                                     .SkipUntil(mouseLeftButtonUp)
                                     
                                     .Let( mm => mm.Zip( mm.Skip( 1 ), ( prev, cur ) =>
                            new
                            {
                                X2 = cur.EventArgs.GetPosition( this ).X,
                                X1 = prev.EventArgs.GetPosition( this ).X,
                                Y2 = cur.EventArgs.GetPosition( this ).Y,
                                Y1 = prev.EventArgs.GetPosition( this ).Y
                            } ) ).Repeat()

                     select pos;




            clickingEvents.Subscribe(
                p =>
                {
                    Line line = new Line();
                    line.StrokeThickness = 2;
                    line.Stroke = new SolidColorBrush( Colors.Black );
                    line.X1 = p.X1;
                    line.Y1 = p.Y1;
                    line.X2 = p.X2;
                    line.Y2 = p.Y2;
                    this.LayoutRoot.Children.Add( line );
                });


                        draggingEvents.Subscribe(
                p =>
                {
                    Line line = new Line();
                    line.StrokeThickness = 2;
                    line.Stroke = new SolidColorBrush( Colors.Red );
                    line.X1 = p.X1;
                    line.Y1 = p.Y1;
                    line.X2 = p.X2;
                    line.Y2 = p.Y2;
                    this.LayoutRoot.Children.Add( line );
                });