IIS 7 Wildcard mapping issues

I recently ran into an issue while converting a site to use the managed pipeline in IIS 7 that took a while to fix but turned out to be one single attribute in web.config. This also turned out to be the answer to something we had simply hacked around before.

I was converting this asp.net website into an application, and configuring it to run under iis 7. The previous developers had setup a url rewriting scheme in global.asax intended to run for extensionless urls such that http:/example.com/placename would properly respond with the information for said place name.

I moved the rewriter logic into a new IHttpModule implementation and configured it in system.webserver. This helped to get my requests mapped properly but the page came up with an error stating: "Session state can only be used when enableSessionState is set to true, either in a configuration file or in the Page directive.". This was an unfortunate error as I had everything already in place for session to work. After a good bit of digging I found that the problem is that when you have a custom module in place to handle all requests you lose the functionality of any other configured module which has a pre-condition for managedHandler. Session is one of these, as is FormsAuthentication.

You can either go through and remove each module and replace with a config that has an empty preCondition attribute, or you can just force all with the following:

<modules runallmanagedmodulesforallrequests="false">

This turned out to be the best option in my case. As I said, this also helped solve an old problem where we would get authentication failures when going to extensionless urls. The behavior is a bit perplexing - logged in when on default.aspx, logged out when at /. It turns out this is the source of that problem too.

The answers are out there, I just had a hell of time finding them so I thought I would re-share.