/// <summary>
        /// check if the url exist in the database
        /// </summary>
        /// <param name="url">the url that must be checked</param>
        /// <returns></returns>
        private ShortURLModel URLExist(string url)
        {
            ShortURLModel foundUrl = _shortUrlRepository.GetByActualUrl(url);

            if (foundUrl != null)
            {
                return(null);
            }
            else
            {
                return(foundUrl);
            }
        }