Update instructions from preview 2 to preview 3 are contained in the download. If you created a project based on the "preview-preview" version, here's what you'll have to update:
Controller The return of a controller action is no longer returned using RenderView(...), but View(...). Alternative return values are View (returns a ViewResult instance), Redirect (redirects to the specified URL and returns a RedirectResult instance), RedirectToAction, RedirectToRoute, Json (returns a JsonResult instance) and Content (which sends text content to the response and returns a ContentResult instance)
View I had to update my ViewData calls as the ViewData property of ViewPage<T> is no longer replaced by T. Instead, you'll have to access your model trough ViewData.Model (where Model is of T).
Routing Routes can now be created using the RouteCollection's extension method "MapRoute". Also, a new constraint has been added to routing where you can allow/disallow specific HTTP methods (i.e. no GET).
Version of assemblies The versions of the System.Web.Abstractions and System.Web.Routing assemblies that are included with the MVC project template have been changed to version 0.0.0.0 to make sure no conflict occurs with the latest .NET Framework 3.5 SP1 Beta release.
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