Have you seen these messages before?
Basically what this means is that you are trying to run two different versions of the .NET framework in the same application pool (process)
The fix is very simple
All we have to do is create a new application pool and make sure that only one version of the .NET framework will run in each version.
How do we do that?
In the IIS Manager we expand the Server Name, and then select the Application Pools node.
Now right click and select New -> Application Pool
We will now create two application pools, one for .NET Framework 1.1 and one for .NET Framework 2.0 applications.
We can normally just select "use default settings for new Application Pool" and give it a name.
So we create the two application pools and they will then show up in the list as shown below.
Note: The only reason we named them .NET Framework 1.1 and .NET Framework 2.0 is so we can identify them.
We so now have to find our applications and set the correct application pool for each application. Most often we will do this only at the Web Site level, but depending on your configuration of web applications you may need to do it for different web applications within the same web site.
There are two steps to this:
- First - set the Application Pool to the correct AppPool
- Second - make sure the correct version of ASP.NET is selected for the application
In the sample above we will want to use the .NET Framework 1.1 - so we select the.NET Framework 1.1 App Pool and next we will make sure that ASP.NET is set to 1.1
Now after these changes we would set the correct configuration for the other web site or web application.
Note: What we have done is make it easier for US to identify if we have the correct AppPool and ASP.NET versions setup but this does not mean you could still not assign the wrong ASP.NET version to the app pool.
Note: It is recommended that you now create an application pool for each web application and not re-use the same AppPools between different web applications