Do I have to use  System.DirectoryServices to check if a my intranet
user is in an AD group?

If so, I'm trying this:

   Dim domainAndUsername As String = Page.User.Identity.Name.ToString
       Dim DirectorySearcher As New
System.DirectoryServices.DirectorySearcher()
       Dim LDAPPATH As String = DirectorySearcher.SearchRoot.Path

       Dim entry As New
System.DirectoryServices.DirectoryEntry(LDAPPATH, domainAndUsername,
"xxxx")

       Dim obj As Object = entry.NativeObject
       Dim search As System.DirectoryServices.DirectorySearcher = New
System.DirectoryServices.DirectorySearcher(entry)
       search.Filter = "(SAMAccountName=yyyy)"
       search.PropertiesToLoad.Add("cn") ' ????
       Dim result As System.DirectoryServices.SearchResult =
search.FindOne()

       If result Is Nothing Then
           Response.Write("Nothing")
       Else
           Response.Write(result.Properties.Item("???").ToString())
       End If

The above is not working, I know it's missing stuff.  I'm not clear on
how to search or what to look for.

Thanks for any help or information.