How to solve “There is a duplicate ‘system.web.extensions/scripting/scriptResourceHandler’” error

 

I got this error after I ran a “C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319>aspnet_regiis –i” command.

Apparently, it happens when you run an older version of ASP.NET application on an IIS server that has been upgraded to use the ASP.NET Framework 4.0.

I found the way to solve this problem via Brad Kingsley’s tip .

All you need to do is to edit your web.config and comment out the section “system.web.extensions” as follows.  It worked well for me, and I hope it does for you too! :)