Getting the business day of the month

I'm working on figuring out what the current 'business' day of the month it is. For instance, if it's the 20th, but there are 3 weekends, it would be the 14th business day of the month.

Is there a better way of doing this?

var first = DateTime.Today.FirstDayOfMonth();
var businessDayOfMonth = 0;
for (var i = first; i <= DateTime.Today; i = i.AddDays(1))
{
    if (i.DayOfWeek != DayOfWeek.Saturday && i.DayOfWeek != DayOfWeek.Sunday) 
        businessDayOfMonth++;
}

As explained in comments (in which I pointed out a few possible edge cases), even though it's not optimized in terms of performance, this is about as clear as it gets.

A more clever algorithm - calculating the number of weekdays without iterating through all of them - is probably possible, but I bet it would be much less readable. If performance isn't a concern at this point, I'd leave it.

You could maybe replace the loop with a LINQ-based solution.

int WhichWorkingDay(DateTime day)
{
    // edge cases
    switch (day.DayOfWeek)
    {
        case DayOfWeek.Saturday:
            return day.Day > 1
                // Friday the day before
                ? WhichWorkingDay(day.AddDays(-1))
                // or next Monday if previous Friday was on last month
                : WhichWorkingDay(day.AddDays(2));
        // analogically here
        case DayOfWeek.Sunday:
            return day.Day > 2
                ? WhichWorkingDay(day.AddDays(-2))
                : WhichWorkingDay(day.AddDays(1));
    }

    // or you could inline it, obviously
    Func isWorkingDay = d => d.DayOfWeek != DayOfWeek.Saturday 
        && d.DayOfWeek != DayOfWeek.Sunday;

    return Enumerable
        .Range(1, day.Day)
        .Select(d => new DateTime(day.Year, day.Month, d))
        .Count(isWorkingDay);
}

StackExchange Code Review Q#124762, answer score: 4