String to DateTime, Tryparse n'était pas suffisant

Voici une méthode qui fonctionne:

        /// <summary>
        /// Checks date validity.
        /// </summary>
        /// <param name="candidate">String to check</param>
        /// <returns>Whether valid and result as a date</returns>
        private static Tuple<bool, DateTime?> ParseDate(string candidate)
        {
            DateTime result;
            if(DateTime.TryParseExact(candidate, "dd.MM.yyyy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "dd.M.yyyy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "dd.MM.yyyy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "d.M.yyyy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "dd/MM/yyyy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "dd/M/yyyy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "dd/MM/yyyy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "d/M/yyyy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "dd.MM.yy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "dd.M.yy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "dd.MM.yy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "d.M.yy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "dd/MM/yy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "dd/M/yy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "dd/MM/yy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result) ||
                DateTime.TryParseExact(candidate, "d/M/yy", CultureInfo.InvariantCulture, DateTimeStyles.None, out result)
            )
            {
                return new Tuple<bool, DateTime?>(true, result);
            }

            return new Tuple<bool, DateTime?>(false, null);
        }