IIS7 deployment - duplicate 'system.web.extensions/scripting/scriptResourceHandler' section

Question

On attempting to deploy a .net 3.5 website on the default app pool in IIS7 having the framework section set to 4.0, I get the following error.

There i

Answer 1

The solution for me was to change the .NET framework version in the Application Pools from v4.0 to v2.0 for the Default App Pool:

Answer 2

In my case it happened after I converted the whole solution (using an extension called Target Framework Migrator) to 4.6.2 but ended up undoing the changes and going back to 3.5 (solution is versioned by TFS). To solve this, I converted just the problematic project (which was using IIS Express to run) to 4.6.2 and then back to 3.5.

Answer 3

In my case I had 2 different apps sharing the same app pool. The first one was using the .net4.5 framwork and the new one was using 2.0. When I changed the second app to it's own app pool it starting working fine with no changes to the web.config.