Application Pooling Gotcha (well it got me….)
Posted by Clayton James on August 11, 2006
What happens when a developer is developing 2.0 web applications using XP IIS 5.0 and the test server is windows 2003 IIS 6.0 and your virtual directory lives in the Default app pool with prevoius 1.0/1.1 web apps?
That’s correct, you receive an error as described below.
Event Type: Error
Event Source: ASP.NET 1.1.4322.0
Event Category: None
Event ID: 1062
Date:
Time:
User: N/A
Computer:
Description:
It is not possible to run two different versions of ASP.NET in the same IIS process. Please use the IIS Administration Tool to reconfigure your server to run the application in a separate process.
This occurs due to the way IIS 6.0 manages a new isolation concept called application pooling, apps that share an application pool can run together in one or more processes. This causes an issue when two apps share the same process but access different versions of the framework.
The simple fix is to create a seperate application pool for 2.0 applications and configure all 2.0 applications to live inside this application pool.
CJ 
EMack said
Ok, so how do I point the new application pool to use the 2.0 framework? I’m trying to install my new 2.0 site on Windows 2003 server. I don’t want to install VS2005 on the QA box.
CJ said
Hi EMack
You will first need to install the 2.0 framework on your QA box so you can configure your 2.0 apps to run against the 2.0 framework.
Once installed, create another application pool which all of your 2.0 sites will be configured to use. To configure your 2.0 virtual directories to use the new application pool, open up the properties of the virtual directory and click the ASP.NET tab. Select the 2.0 runtime. If you don’t see this tab then the 2.0 framework is not installed on the computer.
Hope this helps
CJ