EnsureAuthentication Method
The EnsureAuthentication method of the SPUtility class determines whether the current user is an authenticated user of the specified site and, if not, requests a user name and password, and then opens the Error page for an access denied exception so that the user must request access to the site or list from the owner.
Parameters
web A Microsoft.SharePoint.SPWeb object that represents the site.
Requirements
Platforms: Microsoft Windows Server 2003
Security: Code Access Security