This chapter has covered several advanced extensibility points in the ASP.NET MVC 3 framework. The extensibility points were grouped roughly into three categories, depending on whether they were intending to extend models, views, or controllers (and actions). For models, you learned about the inner workings of value providers and model binders, and examples of how to extend the way MVC handles editing of models through the use of model metadata and model validators. To extend views, you saw how to customize view engines to provide your own conventions about locating view files, as well as two variations of helper methods for generating HTML inside your views. Finally, you learned about controller extensibility through the use of action selectors, action filters, and custom action result types, all providing powerful and flexible ways for uniquely crafting the actions that glue together your models and views. Utilizing these extensibility points can help you bring your MVC application to the next level of functionality and reuse, while also making it easier to understand, debug, and enhance.