/// <summary>
        /// Utility method to fetch an Arena newsletter which corresponds to the given MailChimp List.
        /// </summary>
        /// <param name="listID">List ID of a MailChimp list</param>
        /// <returns>newsletterID of a corresponding Arena newsletter; otherwise returns -1.</returns>
        private int GetNewsletterIDFromMailChimpListID(string listID)
        {
            int newsletterID = -1;
            LookupCollection mailChimpLists = new LookupCollection(new Guid(MailChimpLookupGUIDSetting));
            var query = (from lookup in mailChimpLists.OfType <Lookup>()
                         where lookup.Qualifier == listID
                         select lookup).FirstOrDefault();

            if (query != null)
            {
                newsletterID = int.Parse(query.Qualifier2);
            }
            return(newsletterID);
        }
        /// <summary>
        /// Utility method to fetch an Arena newsletter which corresponds to the given MailChimp List.
        /// </summary>
        /// <param name="listID">List ID of a MailChimp list</param>
        /// <returns>newsletterID of a corresponding Arena newsletter; otherwise returns -1.</returns>
        private int GetNewsletterIDFromMailChimpListID( string listID )
        {
            int newsletterID = -1;
            LookupCollection mailChimpLists = new LookupCollection( new Guid( MailChimpLookupGUIDSetting ) );
            var query = ( from lookup in mailChimpLists.OfType<Lookup>()
                          where lookup.Qualifier == listID
                          select lookup ).FirstOrDefault();

            if ( query != null )
            {
                newsletterID = int.Parse( query.Qualifier2 );
            }
            return newsletterID;
        }