The requested page cannot be accessed because the related configuration data for the page is invalid

I upgraded my SharePoint Foundation farm (there’s only one node) to SharePoint 2010 Server as the time had come in the lifecycle of my proof-of-concept (PoC) to integrate the user profile service application into the mix. The PoC consisted of two web applications over and above the central administration web application: KERBWEB and ADFSWEB. As you can probably guess from the simplistic naming of the web applications one utilises Integrated Windows Authentication (Negotiate (Kerberos), not NTLM) and the other a trusted identity provider (an AD FS claims provider).

After the upgrade my Kerberos-only web application was working fine but my claims-based web application wouldn’t work. The error was:

HTTP Error 500.19 – Internal Server Error

The requested page cannot be accessed because the related configuration data for the page is invalid.

The detailed error information provided me with everything I needed to locate and remedy the issue:

Error code: 0x800700b7

Config Error: Config section ‘appSettings’ already defined. Sections must only appear once per config file. See the help topic <location> for exceptions

Config File: \\?\C:\inetpub\wwwroot\wss\VirtualDirectories\adfsweb.adatum.com80\web.config

Within the detailed error the “config source” section even told me where in the file to look.

Config Source:
801: </location>
802: <appSettings />
803: </configuration>

After staring at the page blankly for about five minutes I realised the obvious. For whatever unknown reason at some point during the upgrade from SharePoint Foundation to SharePoint 2010 Server the applicationHost.config file for the SharePoint web application had managed to get a second, empty, appSettings element inserted right at the end of the file.

Opening the file using elevated credentials I simply commented out the problematic section, saved and reloaded the page (changes are immediate, there’s no need to restart the web site or recycle the application pool) and all was well.

So, the moral of this story is read the detailed error information provided by IIS and if IIS tells you that you have too many <appSettings> nodes you do, so get rid of one of them!

FYI here is what lines 801, 802, 803, 804 and 805 now look like:

801: </location> 
802: <!-- This second appSettings element was mistakenly added by the SP 
803: upgrade and kills the app. commented to fix issue 
804: <appSettings /> --> 
805: </configuration> 

About Paul Williams

IT consultant working for Microsoft specialising in Identity Management and Directory Services.
This entry was posted in SharePoint, Troubleshooting and tagged , , , , , , , . Bookmark the permalink.

4 Responses to The requested page cannot be accessed because the related configuration data for the page is invalid

  1. Thank you! Thank you! thank you… i knew that was the error but was afraid to break it even further by commenting out. I needed “validation” 🙂

  2. Kuik Sok Ping says:

    thank you so much.. you are super!
    yes..there is an extra line added at second last line of the file.

    <!– –>

  3. pheds says:

    Thank you

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