Calculate the number of weekdays between two dates in C#

Question

How can I get the number of weekdays between two given dates without just iterating through the dates between and counting the weekdays?

Seems fairly straightforward

Answer 1

This is an old question but I figured I would share a more flexible answer which allows to removes any day of the week.

I tried to keep the code clean and easy to read while remaining efficient by only looping through 6 days max.

So for the OP you can use it like this:

    myDate.DaysUntill(DateTime.UtcNow, new List { DayOfWeek.Saturday, DayOfWeek.Sunday });


    /// 

    /// For better accuracy make sure  and  have the same time zone.
    /// This is only really useful if we use  - otherwise the computation is trivial.
    /// 
    /// 
    /// 
    /// 
    /// 
    public static int DaysUntill(this DateTime startDate, DateTime endDate, IEnumerable daysOfWeekToExclude = null)
    {
        if (startDate >= endDate) return 0;
        daysOfWeekToExclude = daysOfWeekToExclude?.Distinct() ?? new List();

        int nbOfWeeks = (endDate - startDate).Days / 7;
        int nbOfExtraDays = (endDate - startDate).Days % 7;

        int result = nbOfWeeks * (7 - daysOfWeekToExclude.Count());

        for (int i = 0; i < nbOfExtraDays; i++)
        {
            if (!daysOfWeekToExclude.Contains(startDate.AddDays(i + 1).DayOfWeek)) result++;
        }
        return result;
    }