Profile_OnMigrateAnonymous event firing multiple times

Question

We have an HTTPModule whose sole purpose is to do "url rewriting". By definition of an HTTPModule, ALL browser requests (html, css, javascript, images, etc) go through the event handlers of this class.

During the signin process, we are catching the moment when the user switches from "anonymous" to "signed-in" user in the Global.asax's Profile_OnMigrateAnonymous event handler. One issue we're finding is that when the user signs in, the Profile_OnMigrateAnonymous event fires, seemingly, for possibly EVERY resource within the request to generate the page to the user - namely, the html, css, javascript, images, etc. It was my understanding that this event will fire only ONCE. Why would it be firing multiple times? Is it a result of our registered "url rewriting" HTTPModule? Is there a way we can configure the application to only fire that event once?

Answer 1

For normal resource reqeusts (css/js/img etc) IIS handles the request directly. It only passes to the asp_net worker requests for specfic filenames (such as .aspx and .asmx).

Your HTTPModule is basically forcing IIS to forward all requests to the worker process, hence each request is firing off the Profile_OnMigrateAnonymous.

I don't think you can bypass the call to Profile_OnMigrateAnonymous, however you could implement a bit of code to check for a an .aspx/.ascx etc file name and only then perform the actual actions specified.