这样的算法怎么写

Question

List<DayOfWeek> listWeek = new List<DayOfWeek>();
        listWeek.Add(DayOfWeek.Friday);
        DateTime startTime = new DateTime();
        DateTime endTime = DateTime.Now;
        DateTime currentTime = startTime;
        List<string> listDate = new List<string>();
        while(currentTime < endTime)
        {
            if(listWeek.Contains(currentTime.DayOfWeek))
            {
                listDate.Add(currentTime.ToString("yyyy-MM-dd"));
            }
            currentTime.AddDays(1);
        }

Answer 1

        static void Main(string[] args)
        {
            GetDays(DateTime.Parse("2009-12-1"), DateTime.Parse("2009-12-31"), new DayOfWeek[] { DayOfWeek.Monday, DayOfWeek.Tuesday, DayOfWeek.Wednesday, DayOfWeek.Thursday, DayOfWeek.Friday });
        }        static void GetDays(DateTime dtStart, DateTime dtEnd, DayOfWeek[] days)
        {
            for (DateTime dt = dtStart; dt <= dtEnd; dt = dt.AddDays(1))
            {
                bool b = false;
                for (int i = 0; i < days.Length; i++)
                {
                    if (days[i] == dt.DayOfWeek)
                    {
                        b = true;
                        break;
                    }
                }
                if (b)
                    Console.WriteLine(dt.ToString("yyyy-MM-dd"));
            }
        }