Implementing a contact form plugin for ASP.NET MVC

The purpose of this post is to demonstrate the patterns presented in the Patterns for ASP.NET MVC Plugins series so far.

1. Routes, Controllers and Configuration
2. View Models
3. Demo: Implementing a contact form plugin

I've chosen the contact form scenario because it's a very common requirement most developers are familiar with. Also, the implementation is short and straightforward. The idea is that you focus on the patterns rather than the actual functionality of the plugin. The same patterns can be used to implement more interesting plugins.