Custom HttpModules and AJAX errors

Seems like all I do lately is fix other people’s GA plugins. This one is really handy though. It creates a pluggable HttpModule to insert the GA script on all your ASPX pages. I found the original post here:

First thing I noticed was the Google script is out of date which was easy enough to fix. More recently. I found out it also doesn’t play nice with things like AJAX which apparently trigger HttpApplication.BeginRequest a whole lot. I received this error on one of my pages that uses AJAX.

Unfortunately, the suggested solutions are many fold, most likely because the causes of that particular error are many fold. In my case it was the HttpModule. The thing is, I couldn’t just turn it off, my client likes the GA statistics as much as I do.

To fix this all you need to do is make sure the module logic is _only _fired if the source of event is an .aspx page. The relevant code looks like this:

void OnBeginRequest(object sender, EventArgs e)
  //only if the request comes from an .aspx page
  if (HttpContext.Current.Request.Path.ToLower().IndexOf(".aspx") > -1)
    application.Response.Filter = new AnalyticsStream(application.Response.Filter, accountNumber);

This like will solve similar problems with other IHttpModule implementations out there too.

You can get the source for the fixed Clarius.GoogleAnalytics module here:

Edit: Removed link, sorry the file was lost in a blog move.

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