The ASP.NET MVC team is in the final stages of finishing up a new "Preview 4" release that they hope to ship later this week. The Preview 3 release focused on finishing up a lot of the underlying core APIs and extensibility points in ASP.NET MVC. Starting with Preview 4 this week you'll start to see more and more higher level features begin to appear that build on top of the core foundation and add nice productivity. There are a bunch of new features and capabilities in this new build - so much in fact that I decided I needed two posts to cover them all. This first post will cover the new Caching, Error Handling and Security features in Preview 4, as well as some testing improvements it brings. My next post will cover the new AJAX features being added with this release as well.