What should my ASP.NET MVC Controllers represent - "real world" application.

Question

I have an established web application built as an ASP.NET 3.5 Web App. We recently modified it to mix MVC into the app for some new functionality.

Now that it's in there, we want to leverage MVC wherever possible to begin to "transform" the app from clunky webforms to a more maintainable and testable MVC app.

The question that just came up in adding some new functionality is what controller should be responsible for a certain action.

Let me be more detailed.

The scenario involves at least three major conceptual areas in our app. The app needs to be able to set their PREFERENCE for a default MAP view while they are on a SEARCH screen. Preferences, Maps and Search are all major concepts in our system. Furthermore, this preference setting (basically, where should the map start out) may be used to set the initial map in more than one search page (it's basically a search preference).

The existing MVC controller in the app is a MAPCONTROLLER, with 3 actions that are responsible for generating HTML or JSON data to put on a map.

What we need to do now, is add an MVC route (controller + action) to allow the client view to save some information as their preference. Basically, whenever they are on the search page looking at a map, they can click a button that says "remember this as my default map view", and from then on, their map will always start with that view.

My question is (and I apologize, but I wanted to be very very clear, I see too many questions with no context to help). What should my controller represent? I obviously have 3 major system areas involved. Would it be proper to create a new SEARCH or PREFERENCES controller with a SaveDefaultMapView action (no view required), or piggyback on the xisting MAP controller, even though this new function is more about search and preferences than actual map generation? Should an MVC controller be aligned mostly with the screen (search page/search subsystem), the domain / data being manipulated (preferences), or the very specific visual element under scrutiny at the time the action is taken (the map)?

All of the examples and bootcamp projects are all well and good, but they are far too clean and simplified to apply to a huge legacy app. How does one design their MVC components around a system that incorporates many domain concerns into a single webpage?

Thanks all!

Answer 1

There are no hard and fast rules for how the controllers are organized. You organize them the way it makes most logical sense to you. This will require a bit of experimentation as you see how the routing works out, and you find the cleanest, most elegant design.

ASP.NET MVC is brilliantly agnostic in this respect. It doesn't care how you design your controller/route substructure, and it is flexible enough to handle most any design.

Your application design should be heavy on the Model side. Your controllers should be relatively small; if you find that you are stuffing a large amount of logic in the controllers, you should refactor that logic to the model, or add a service layer to contain the logic. Your controller layer is best thought of as a "patch panel"; it is the place where you connect your incoming Urls via routes to your model/service layer and your View Model/Views.

You should definitely check out Project Areas, as this might be an appropriate mechanism to contain your three different system areas.

Answer 2

Thanks, Robert. I guess I could rephrase a bit...what guidelines have others found to be useful for keeping their controller responsibilities organized and logical? While my example above only touches 3 of our areas, I expect to eventually replace most/all of the application with MVC. Furthermore, each of the 3 areas I mentioned has relationships to multiple other areas.(eg, maps can be used to plot several location-based entities, preferences can apply to any area of the system, and, like maps, is capable of searching for several kinds of business entities (one at a time, not all together). So the lines are blurry. I'm interested in hearing how others have found workable guidelines for controller organization. Oh, and at the very least, we are sticking to the skinny controller/fat model paradigm!