business_days.rb

def working_days(start_date, end_date)
	days = []
	(start_date..end_date).each { |d| days << d if d.cwday < 6 }
	days
end

working_days(Date.today, Date.today + 7).each{|x| puts x.to_s}

BusinessDays.cs

public static class BusinessDays
{
    public static bool WorkingDay(this DateTime date)
    {
        return date.DayOfWeek != DayOfWeek.Saturday && date.DayOfWeek != DayOfWeek.Sunday;
    }

    /*  this function is used only to collect the dates
        we are not paying much attention of the implementation */
    public static List<DateTime> GetAlldates(DateTime start, DateTime end)
    {
        List<DateTime> dates = new List<DateTime>();
        DateTime currLoopDate = start;            
        while (currLoopDate < end)
        {
            dates.Add(currLoopDate);
            currLoopDate = currLoopDate.AddDays(1);
        }
        return dates;
    }
}

var dates = BusinessDays.GetAlldates(DateTime.Now, DateTime.Now.AddDays(7)); 
int getBizDays = dates.Where(day => day.WorkingDay()).Count();