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ASP.NET MVC 3: Global action filters

ASP.NET MVC 3 supports global action filters. Global action filters are applied to all actions in web application. By example, you can use global action filters for common security checks. In this posting I will show you how to write dummy action filter, register it as global and test it.

Source code

You can find source code of this example from Visual Studio 2010 experiments repository at GitHub.

Source code @ GitHub Source code repository
GitHub

Example is located in Experiments.AspNetMvc3NewFeatures.GlobalActionFilters project.

Creating action filter

Let’s start with our primitive action filter that is able in some cases ruin page layout for IE. Am I evil? Yes, I am! But I want this example to work on IIS and Cassini both so let’s make something trivial.


public class MyActionFilterAttribute : ActionFilterAttribute
{
    public override void OnResultExecuting(ResultExecutingContext context)
    {
        base.OnResultExecuting(filterContext);

        context.RequestContext.HttpContext.Response.Write("<!-- Buuu! -->");
    }
}

All this evil filter does is it writes string <!—Buuu! –> to response stream, so it is the first line of output.

Global action filters: no filters yetNow open one of your ASP.NET MVC projects and run it. It does not matter if you run it on IIS or Cassini (ASP.NET development web server). If you look at page source you should see usual HTML there. Something like you see on image on right.

Registering global action filter

Now, without touching any controller let’s put our evil Buuu! in place. Open global. asax and modify Application_Start event so it looks like follows.


protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();

    // Register global filter
    GlobalFilters.Filters.Add(new MyActionFilterAttribute());
   
    RegisterGlobalFilters(GlobalFilters.Filters);
    RegisterRoutes(RouteTable.Routes);
}

Compile your project and run application again. Now you should see output like this.

Global action filters: evil filter is registered

Without any additional modification to controllers and their methods we got our action filter work for all controllers. You can surf around your site and for every request you should see now my evil message.

Conclusion

Global application filters are powerful and easy to use features. You can use global filters for different purposes like establishing global security policies and controlling output. Of course, you may find many other uses for global action filters. ASP.NET MVC makes is very easy to register filters at global level and I think it is another great addition to MVC framework.

Posted: Aug 15 2010, 12:03 AM by DigiMortal | with 17 comment(s)
Filed under: ,

Comments

TJ said:

Thanks for an idea. I have an application that needs to be https always and this is a great starting point for me.

# May 14, 2011 12:20 AM

Saeed Neamati said:

Very simple, yet powerful explanation of the Global Action Filter concept. Thanks. I wish you had kind of Google+ on your page, so that we could easily share your articles.

# November 16, 2011 3:12 AM

Saeed Neamati said:

ASP.NET MVC Filters are one of the greatest features of ASP.NET MVc, and I think the reason is that, you can get a strategic point in response, where everything is in your control (a centralized place) to do whatever you like.

However, getting the result HTML (what that is being sent back to the user) is not a neat, clean, straightforward matter. I think explaining a little about that would be a good idea in general.

Thanks.

# April 26, 2012 10:57 AM