Tips and Tricks

Implementing Default Behavior in an ASP.NET MVC Controller

If there's something you want to do every time an Action method is called in a Controller, there's an easy way to achieve that. It may even be a best practice.

Every Controller class has a method called OnActionExecuting that runs before any Action method is called (there's also an OnActionExecuted that runs after any Action method). If you wanted to implement some logging code to keep track of a Controller's behavior, OnActionExecuting would be a great place to put your logging code:

Public Class HomeController
  Inherits System.Web.Mvc.Controller

  Protected Overrides Sub OnActionExecuting(filterContext As ActionExecutingContext)
    '... logging code ...
    MyBase.OnActionExecuting(filterContext)
  End Sub

Of course, if you wanted to apply this code on only some methods in some controllers, you could create an Action Filter. But what if you wanted to apply this code to every action method in every controller? You have two choices.

You could, of course, create an Action Filter and apply it through the GlobalFilterCollection in the FilterConfig class in your application's App_Start folder. Or you could create a base Controller class to hold the method:

Public Class ControllerBase
  Inherits System.Web.Mvc.Controller

  Protected Overrides Sub OnActionExecuting(filterContext As ActionExecutingContext)
    MyBase.OnActionExecuting(filterContext)
  End Sub

End Class

And then have all your other controllers inherit from your new base Controller class:

Public Class HomeController
  Inherits ControllerBase

Personally, I think it's a good idea to have your own base class for your Controllers. You may not need it yet, but when you do have some code you want to share with all your Controllers, you'll be glad that base class exists.

About the Author

Peter Vogel is a system architect and principal in PH&V Information Services. PH&V provides full-stack consulting from UX design through object modeling to database design. Peter tweets about his VSM columns with the hashtag #vogelarticles. His blog posts on user experience design can be found at http://blog.learningtree.com/tag/ui/.

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