/// <summary>
        /// Removes the supplied share from the watchlist.
        /// </summary>
        /// <param name="userId">The unique identifier of the user who owns the watchlist.</param>
        /// <param name="watchlistId">The unique identifier of the watchlist.</param>
        /// <param name="symbol">The share symbol.</param>
        private Watchlist GetWatchlist(Guid userId, Guid watchlistId)
        {
            Watchlist watchlist = _watchlistRepository.GetById(watchlistId);

            if (watchlist == null || watchlist.UserId != userId)
            {
                throw new EntityNotFoundException(nameof(Watchlist), watchlistId);
            }

            return(watchlist);
        }