Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Since .NET 4 is backward compatible, can't all app pools be set to use .NET 4 without changing your web site? Or will web.config's need to be updated simply from the app pool change?

share|improve this question
up vote 1 down vote accepted

There are certain cases where you will need to update your web.config, in particular when using .NET 3.5 you will need to clear the web.config from all the section definitions that were added to it, for things like System.Web.Extensions or otherwise you will run into errors in the configuration telling you duplicate items in the collection.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.