Prevent IIS from serving static files through ASP.NET pipeline

Question

Requests for my css, js, image files are being served through the ASP.NET pipeline. I thought IIS by default avoided this, but I see the requests on my Application_AuthenticateRequest breakpoint and there's no need to actually authenticate those requests. I've seen conflicting approaches to change this behavior - What is the best way to do this?

Answer 1

I'm taking a guess here and suspect that you have the following setting configured in your web.config file:

<modules runAllManagedModulesForAllRequests="true">

This means that every request, including those for static content is hitting the pipeline.

Change this setting to:

<modules runAllManagedModulesForAllRequests="false">

This is assuming your application is running under ASP.NET 4.0 and MVC3.

For this to work you need to install KB980368 (requires a reboot) or Windows 2008R2 SP1 (which includes this hotfix). The reason for this is explained in this excellent article:

How ASP.NET MVC Routing Works and its Impact on the Performance of Static Requests

Answer 2

I ended up adding this to my web.config. I know all my static files will exist in these folders, so it works ok for my needs.

<location path="scripts">
    <system.web>
        <authentication mode="None" />
        <authorization>
            <allow users="*" />
        </authorization>
    </system.web>
</location>
<location path="styles">
    <system.web>
        <authentication mode="None" />
        <authorization>
            <allow users="*" />
        </authorization>
    </system.web>
</location>
<location path="images">
    <system.web>
        <authentication mode="None" />
        <authorization>
            <allow users="*" />
        </authorization>
    </system.web>
</location>

Answer 3

In VS2012 /MVC3 with the Visual Studio Development Server enabled, the RAMMFAR=false has no effect. Each request for static files still hits the Application_BeginRequest event handler.

I switched over to IIS Express and saw the desired functionality.

Answer 4

Somewhere in either your IIS configuration, or a web.config, you have a handler mapping set up to map these files to your ASP.Net application.

Try deleting your web.config and see if you can still browse to these file types from within IIS without ASP.Net. If that fails you'll know it's your web.config - otherwise you'll have to check the IIS settings.

Step 2 - Put the web.configs back, then delete and recreate the site - same problem? It's a setting in the root of IIS which means it applies to all sites - check the handler mappings here.