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

Utility functions to get a range of dates:

public IEnumerable GetDates(DateTime begin, int count)
{
    var first = new DateTime(begin.Year, begin.Month, begin.Day);
    var maxYield = Math.Abs(count);
    for (int i = 0; i < maxYield; i++)
    {
        if(count < 0)
            yield return first - TimeSpan.FromDays(i);
        else
            yield return first + TimeSpan.FromDays(i);      
    }
    yield break;
}

public IEnumerable GetDates(DateTime begin, DateTime end)
{
    var days = (int)Math.Ceiling((end - begin).TotalDays);
    return GetDates(begin, days);
}

LINQPad demo code:

var begin = DateTime.Now;
var end = begin + TimeSpan.FromDays(14);

var dates = GetDates(begin, end);
var weekdays = dates.Count(x => x.DayOfWeek != DayOfWeek.Saturday && x.DayOfWeek != DayOfWeek.Sunday);
var mondays = dates.Count(x => x.DayOfWeek == DayOfWeek.Monday);
var firstThursday = dates
    .OrderBy(d => d)
    .FirstOrDefault(d => d.DayOfWeek == DayOfWeek.Thursday);

dates.Dump("Dates in Range");
weekdays.Dump("Count of Weekdays");
mondays.Dump("Count of Mondays");
firstThursday.Dump("First Thursday");