Flashing a graphic in the ESRI Silverlight API

Being able to flash a shape on the map is a nice usability feature in GIS applications to relate shapes on the map to attributes in a data table or data grid. Also, most GIS users have gotten used to the feature in ArcMAP. I had written up an extension method to the Graphic class in the ESRI Silverlight API to be able to do this easily with a simple function call. Here is the code for the extension method.

        public static void Flash( this Graphic graphic )

        {

            Flash( graphic, 200, 10 );

        }

 

        public static void Flash( this Graphic graphic, double milliseconds, int repeat )

        {

            int count = 1;

            repeat = repeat * 2;

            Symbol tempSymbol = graphic.Symbol;

            Storyboard storyboard = new Storyboard();

            storyboard.Duration = TimeSpan.FromMilliseconds( milliseconds );

            graphic.Symbol = null;

            storyboard.Completed += ( sender, e ) =>

            {

                if( count % 2 == 1 )

                    graphic.Symbol = tempSymbol;

                else

                    graphic.Symbol = null;

 

                if( count <= repeat )

                    storyboard.Begin();

 

                count++;

            };

            storyboard.Begin();

        }

 

After including the above extension method in your project just call the ‘Flash’ method on the graphic object

graphic.Flash();

Note that I am using the Storyboard as the timer which is preferred over of the DispatcherTimer.

This has also been added to the ESRI Silverlight API Contrib project here.