I have modified an example form the script.aculo.us [1] web site that is showing some effects for a shopping cart web application. The example is using a generic dictionary (Dictionary<string,int>) to store the article and count in a session variable. Note: you must use the latest version of Ajax.NET Professional [2] (6.5.17.1 or higher).
The demo is available at http://www.ajaxpro.info/shop/ [3].