usergroup.GetAllUserCollectionFromWeb method is returning non-site users

Question

I'm using the UserGroup.GetAllUserCollectionFromWeb method to return all the users in a Site Collection: https://msdn.microsoft.com/en-us/library/websvcusergroup.usergroup.getallusercollectionfromweb(v=office.14).aspx

When used, the result set includes users that are no longer in the site and or can't be validated through the Check Permissions modal. (Site Actions --> Site Permissions --> Check Permissions).

Result set:
userA (valid)
userB (can't validate in modal)
userC (valid)
userD (valid)

Answer 1

Even if user no longer valid they still exist in user information list. To permanently delete user from site collection, follow below steps:

1. On the site collection home page, click the Site Actions menu, point to Site Settings, and then click People and Groups.
2. On the People and Groups page, in the Quick Launch, click All People.
3. On the People and Groups: All People page, select the check box next to the user who you want to delete.
4. On the Actions menu, click Delete Users from Site Collection, and then click OK.

For more information, you can check below links:

https://support.office.com/en-us/article/Remove-users-and-groups-from-site-access-8a221be7-3696-4e28-9cfb-76532dce3563

http://iedaddy.com/2010/12/sharepoint-2010-deleted-and-recreated-user-doesnt-have-permissions-to-site-access-denied/