MvcContrib.CommandProcessor.Validation.Rules.DateComesBeforeHelper.IsValid C# (CSharp) Method

        public static string IsValid(DateTime? earlierDate, DateTime? laterDate)
        {
            DateTime nonNullEarlierDate = earlierDate ?? DateTime.MinValue;
            DateTime nonNullLaterDate = laterDate ?? DateTime.MaxValue;

            if (nonNullLaterDate.Hour == 0 && nonNullLaterDate.Minute == 0)
                nonNullLaterDate = nonNullLaterDate.AddDays(1).Subtract(new TimeSpan(0, 0, 1, 0));

            if (nonNullEarlierDate.Date == nonNullLaterDate.Date && nonNullLaterDate.Date != nonNullLaterDate &&
                nonNullEarlierDate > nonNullLaterDate)
            {
                return "Time on {0} cannot precede time on {1}";
            }

            if (nonNullEarlierDate > nonNullLaterDate)
            {
                return "{0} cannot precede {1}";
            }

            return null;
        }

        public static string IsValid(DateTime?earlierDate, DateTime?laterDate)
        {
            string isValid = DateComesBeforeHelper.IsValid(laterDate, earlierDate);

            if (isValid != null)
            {
                isValid = isValid.Replace("cannot precede", "cannot be after");
            }

            return(isValid);
        }