I'm having a problem trying to add an ASP.NET Membership (SQL Provider) user as a site collection administrator in WSS3.

My user can log into the front end website and can manage their profile (modify and save) using my custom forms, so the actual FBA/ASP.NET Membership system seems to be working correctly.

When I browse to the Site Collection Administrators screen (within the site collection, logged in as a different admin user) and enter the name of my user as 'myprovider:myusername', and then click the Check Names button, the user is validated and it appears that the system has recognised it.

However, when I click OK to add the user as an administrator, I get the following error:

The user or group 'myprovider:myusername' is unknown. at Microsoft.SharePoint.Utilities.SPUtility.FilterValidLoginName(String loginName, SPSite site)

Does anyone know why this might be?

  • 2
    Did you add FBA settings to Central Administration site? Jul 26 '11 at 11:19
  • I'm hoping this could be the solution, waiting on hearing back from another developer to see if it has worked. Jul 29 '11 at 13:18
  • This was the cause, once I had the Central Admin set up correctly I was able to add users. Thanks for the pointer. Aug 4 '11 at 9:32

When configuring FBA it is important to also set Central Administration site and SecurityTokenServiceApplication by using exactly the same settings as on FBA enabled web application.

Details of how to configure FBA can be found here:


If your web application is set to use Claims Based Authentication with FBA or with some other custom claims enabled it is also common for PeoplePicker control to mark every input as resolved (without actually checking for user) and this can be confusing and can lead to errors as described in this question.

Some more info on PeoplePicker can be found by exploring following links:




  • I just posted my comment as answer and added some extra info. Aug 4 '11 at 10:28

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