ASP.NET MVC: Putting Your Controllers In A Separate Assembly

Having been a part of many large enterprise ASP.NET MVC application implementations using test driven development I learned early on that separating your controller classes into a their own project significantly reduces the noise in your web project.  It wasn’t until a recent talk I gave to user group in my region that I realized that this isn’t a widely adopted practice.  For large applications with a lot of developers and a complex architecture I highly recommend it. 

Putting your controllers in a separate assembly is very straight forward.  First create a controllers project in your solution and then you just need to update your route registrations to tell them where to look for the controllers.

1. routes.MapRoute(name: "Default", url: "{controller}/{action}/{id}",
2.                 namespaces: new[] {"[Namespace of the Project that contains your controllers]"},
3.                 defaults: new {controller = "Home", action = "Index", id = UrlParameter.Optional});

In order to tell ASP.NET MVC where to look for your controllers when registering your routes you use the ‘namespaces’ parameter of the MapRoute method as illustrated above.

I know that the concept of putting controllers in a separate assembly is a bit controversial and everyone seems to have a strong opinion either for or against, so let me know what side of the fence you fall on.