In Preview 2 or Preview 3 of ASP.NET (I forget which), we introduced the concept of Action Filters . Sounds much more exciting than your run-of-the-mill LayOnTheCouchMunchingChipsWatchingInfomercialsFilter , that I originally proposed to the team. Thankfully, that was rejected. An action filter is an attribute you can slap on an action method in order to run some code before and after the action method executes. Typically, an action filter represents a cross-cutting concern to your action method. Output caching is a good example of a cross-cutting concern. In CodePlex Preview 4 of ASP.NET MVC , we split out our action filters into four types of filters, each of which is an interface. IAuthorizationFilter IActionFilter IResultFilter IExceptionFilter…(read more)