Import from AD to Sharepoint Group All Users

public static void Import(string username, string domain,string completeDomain)
    {
        PrincipalContext ctx = new PrincipalContext(ContextType.Domain, completeDomain);
        Console.WriteLine(ctx.Name + " --> " + ctx.UserName + " --> " + ctx.ConnectedServer);
        Console.ReadKey();

        UserPrincipal findAllUser = new UserPrincipal(ctx);

        PrincipalSearcher ps = new PrincipalSearcher(findAllUser);

        try
        {
            Microsoft.SharePoint.SPSecurity.RunWithElevatedPrivileges(delegate()
                 {
                     using (SPSite elevatedSite = new SPSite(GetUrl()))
                     {
                         using (SPWeb web = elevatedSite.OpenWeb())
                         {
                             foreach (Principal user in ps.FindAll())
                             {
                                 web.AllowUnsafeUpdates = true;
                                 elevatedSite.AllowUnsafeUpdates = true;

                                 Console.WriteLine(user.Name + "-->" + user.DistinguishedName);
                                 Console.ReadKey();

                                 var loginName = domain + "\\" + user.SamAccountName;
                                 var name = user.DisplayName;
                                 web.AssociatedVisitorGroup.Users.Add(loginName, string.Empty, name, string.Empty);

                             }
                         }

                     }
                 });
        }
        catch (Exception exx)
        {
            Console.WriteLine(exx.Message);
            Console.WriteLine(exx.StackTrace);
            Console.ReadKey();
        }
        Console.ReadLine();
    }