This topic contains a brief description about ASP.NET MVC. If you are looking for ASP.NET MVC Hosting, you can always consider ASPHostCentral and you can start from our lowest Standard Plan @$4.99/month to host your .NET MVC site.

One of the main design principles ASP.NET MVC has been designed with is extensibility. Everything (or most of) in the processing pipeline is replaceable so, if you don’t like the conventions (or lack of them) that ASP.NET MVC uses, you can create your own services to support your conventions and inject them into the main pipeline.

In this post we are going to show 13 extensibility points that every ASP.NET MVC developer should know, starting from the beginning of the pipeline and going forward till the rendering of the view.

1. RouteConstraint

Usually you could put some constrains on url parameters using regular expressions, but if your constrains depend on something that is not only about the single parameter, you can implement the
IRouteConstrains’s method and put your validation logic in it.

One example of this is the validation of a date: imagine an url that has year, month and date on different url tokens, and you want to be able to validate that the three parts make a valid date.

2. RouteHandler

Not really specific to ASP.NET MVC, the
RouteHandler is the component that decide what to do after the route has been selected. Obviously if you change the RouteHandler you end up handling the request without ASP.NET MVC, but this can be useful if you want to handle a route directly with some specific HttpHanlders or even with a classic WebForm.

3. ControllerFactory

The controller factory is the component that, based on the route, chooses which controller to instantiate and instantiate it. The default factory looks for anything that implements
IController and whose name ends with Controller, and than create an instance of it through reflection, using the parameter-less constructor.

But if you want to use Dependency Injection you cannot use it, and you have to use a IoC aware controller factory: there are already controller factory for most of the IoC containers. You can find them in MvcContrib or having a look at the Ninject Controller Factory.

4. ActionInvoker

ActionInvoker is responsible for invoking the action based on it’s name. The default action invoker looks for the action based on the method name, the action name and possibly other selector attributes. Then it invokes the action method together with any filter defined  and finally it executes the action result.

If you read carefully you probably understood that most of the execution pipeline is inside the logic of the default
ControllerActionInvoker class. So if you want to change any of these conventions, from the action method’s selection logic, to the way http parameters are mapped to action parameters, to the way filters are chosen and executed, you have to extend that class and override the method you want to change.

5. ActionMethodSelectorAttribute

Actions, with the default action invoker, are selected based on their name, but you can finer tune the selection of actions implementing your own Method Selector. The framework already comes with the
AcceptVerbs attribute that allows you to specify to which HTTP Verb an action has to respond to.

A possible scenario for a custom selector attribute is if you want to choose one action or another based on languages supported by the browser or based on the type of browser, for example whether it is a mobile browser or a desktop browser.

6. AuthorizationFilter

These kind of filters are executed before the action is executed, and their role is to make sure the request is “valid”.

There are already a few Authorization filters inside the framework, the most “famous” of which is the
Authorize attribute that checks whether the current user is allowed to execute the action. Another is the the ValidateAntiForgeryToken that prevents CSRF attacks. If you want to implement your own authorization schema, the interface you have to implement is IAuthorizationFilter. An example could be the hour of the day.

7. ActionFilter

Action Filters are executed before and after an action is executed. One of the core filters is the
OutputCache filter, but you can find many other usages for this filter. This is the most likely extension point you are going to use, as, IMHO, it’s critical to a good componentization of views: the controller only has to do its main stuff, and all the other data needed by the view must be retrieved from inside action filters.

8. ModelBinder

The default model binder maps HTTP parameters to action method parameters using their names: a http parameter named will be mapped to the City property of the Address object that itself is a property of the method parameter named user. The
DefaultModelBinder works also with arrays, and other list types.

But it can be pushed even further: for example you might use it to convert the id of the person directly to the Person object looking up on the database. This approach is explained better in the following post Timothy Khouri (aka SingingEels): Model Binders in ASP.NET MVC. The code is based on the preview 5, but the concept remains the same.

9. ControllerBase

All controllers inherit from the base class
Controller. A good way to encapsulate logic or conventions inside your actions is to create you own layer supertype and have all your controllers to inherit from it.

10. ResultFilter

Like the ActionFiters, the ResultFilters are execute before and after the ActionResult is executed. Again, the OutputCache filter is an example of a ResultFilter. The usual example that is done to explain this filter is logging. If you want to log that a page has been returned to the user, you can write a custom RenderFilter that logs after the ActionResult has been executed.

11. ActionResult

ASP.NET MVC comes with many different kind of results to render views, to render JSON, plain text, files and to redirect to other actions. But if you need some different kind of result you can write your own
ActionResult and implement the ExecuteResult method. For example, if you want to send a PDF file as result you could write your own ActionResult that use a PDF library to generate the PDF. Another possible scenario is the RSS feed: read more about how to write a RssResult in this post.

Look at implementing a custom action result when the only peculiarity is how the result is returned to the user.

12. ViewEngine

Probably you are not going to write your own view engine, but there are a few that you might consider using instead of the default WebForm view engine.

13. HtmlHelper

Views must be very dumb and thin, and they should only have html markup and calls to HtmlHelpers. There should be no code inside the views, so helpers come very handy for extracting the code from the view and putting it into something that is testable.

Top Reasons to trust your ASP.NET MVC website to

What we think makes so compelling is how deeply integrated all the pieces are. We integrate and centralize everything--from the systems to the control panel software to the process of buying a domain name. For us, that means we can innovate literally everywhere. We've put the guys who develop the software and the admins who watch over the server right next to the 24-hour Fanatical Support team, so we all learn from each other:

- 24/7-based Support - We never fall asleep and we run a service that is operating 24/7 a year. Even everyone is on holiday during Easter or Christmas/New Year, we are always behind our desk serving our customers
- Excellent Uptime Rate - Our key strength in delivering the service to you is to maintain our server uptime rate. We never ever happy to see your site goes down and we truly understand that it will hurt your onlines business. If your service is down, it will certainly become our pain and we will certainly look for the right pill to kill the pain ASAP
- High Performance and Reliable Server - We never ever overload our server with tons of clients. We always load balance our server to make sure we can deliver an excellent service, coupling with the high performance and reliable server
- Experts in ASP.NET MVC Hosting - Given the scale of our environment, we have recruited and developed some of the best talent in the hosting technology that you are using. Our team is strong because of the experience and talents of the individuals who make up ASPHostCentral
- Daily Backup Service - We realise that your website is very important to your business and hence, we never ever forget to create a daily backup. Your database and website are backup every night into a permanent remote tape drive to ensure that they are always safe and secure. The backup is always ready and available anytime you need it
- Easy Site Administration - With our powerful control panel, you can always administer most of your site features easily without even needing to contact for our Support Team. Additionally, you can also install more than 100 FREE applications directly via our Control Panel in 1 minute!

Happy hosting!