Error Deploying ASP.NET 2.0 Application

Recently I rebuilt one of my primary servers (and redeployed it with a new co-lo host here in Calgary), so admittedly I haven't worked through all the configuration quirks yet (but that's no excuse).

The new Server is running Windows 2003 with IIS 6.0 and has several ASP.NET 1.1 applications.

Well yesterday, I deployed a new website for some friends and a good cause. And had decided to create the website as my first little ASP.NET 2.0 web application project. I set it up using basic default settings in the IIS Console. The website crashed upon first load of course, displaying a general Server Error message. I then quickly discovered some of my other ASP.NET 1.1 applications where hanging, not loading at all, with no error message - just hanging.

The general Server Error message I got suggested looking at the Event Viewer, where I found the following message.

"It is not possible to run two different versions of ASP.NET in the same IIS process."

Although it doesn't say it directly, I suspected the process the message was referring to was the Application Pools.

I created a new Application Pool in the IIS Console (with default settings) and named it "Version 2 Pool", and then went to the properties dialog of the IIS Console for my ASP.NET 2.0 application and changed the Application Pool assignment.

This fixed my ASP.NET 2.0 website, but my other ASP.NET 1.1 websites that were sharing the "DefaultAppPool" Application Pool were still not loading.

Back in the Application Pool section of the IIS Console I simply tried recycling "DefaultAppPool" to clear whatever was preventing the sites from loading. This did the trick.

What's the lesson to be learned here? Pay more attention to the importance of the Application Pools, and not just to avoid errors like this - but to take advantage of the them to improve performance and reliability.

Thanks for reading.