c# - How to get the next working day, excluding weekends and holidays

Question

I have a requirement where I need to work on a date field, so the requirement is some thing like this

I will call the field as minimum possible date

1. Add +1 to the date

2. If the minimum possible date happens to fall on a weekend(Sat or Sun) after adding 1 day, Display the next working day i.e Monday

3. If the?minimum possible date happens to fall on a Holiday, display the next working day. (Holidays?1.1?, 1.5?, 3.10?, 25.12?, 26.12)

4. If the minimum possible date happens to fall on a weekend(Sat or Sun) after adding 1 day, and the day after that is a holiday then show the next working day. Eg: After +1 day if min possible day is Saturday, we will have to display Monday. But if Monday happens to be a Holiday then we have to display Tuesday.

I have tried a solution to the above problem by having multiple if and else cases, but just wondering if there is any generic and graceful way of doing it?

I have tried

var Holidays = new List<DateTime>();
Holidays.Add(new DateTime(DateTime.Now.Year,1,1));
Holidays.Add(new DateTime(DateTime.Now.Year,1,5));
Holidays.Add(new DateTime(DateTime.Now.Year,3,10));
Holidays.Add(new DateTime(DateTime.Now.Year,12,25));

if(date.DayOfWeek === DayOfWeek.Saturday || date.DayOfWeek === DayOfWeek.Sunday)

{

     //Logic to add +1 and again some logic to check for weekends and weekdays
}


else if(holidays.Contain(date))
{

   //Logic to add +1 and again some logic to check for weekends and weekdays
}

Answer 1

Basically you want to get the next working day. So you could loop on this condition adding 1 day to the current date

do {
  date = date.AddDays(1);
} while(IsHoliday(date) || IsWeekend(date));

In the previous code IsHoliday is a predicate telling if a date is holiday. For instance, shamelessly reusing your code:

class Program
{
    private static readonly HashSet<DateTime> Holidays = new HashSet<DateTime>();

    private static bool IsHoliday(DateTime date)
    {
        return Holidays.Contains(date);
    }

    private static bool IsWeekend(DateTime date)
    {
        return date.DayOfWeek == DayOfWeek.Saturday
            || date.DayOfWeek == DayOfWeek.Sunday;
    }


    private static DateTime GetNextWorkingDay(DateTime date)
    {
        do
        {
            date = date.AddDays(1);
        } while (IsHoliday(date) || IsWeekend(date));
        return date;
    }

    static void Main(string[] args)
    {
        Holidays.Add(new DateTime(DateTime.Now.Year, 1, 1));
        Holidays.Add(new DateTime(DateTime.Now.Year, 1, 5));
        Holidays.Add(new DateTime(DateTime.Now.Year, 3, 10));
        Holidays.Add(new DateTime(DateTime.Now.Year, 12, 25));

        var dt = GetNextWorkingDay(DateTime.Parse(@"2015-10-31"));

        Console.WriteLine(dt);

        Console.ReadKey();
    }
}