C# get Last day Of Month หาวันสุดท้ายของเดือนครับ (End Day Of Month)

DateTime today = DateTime.Today;
DateTime endOfMonth = new DateTime(today.Year, today.Month, DateTime.DaysInMonth(today.Year, today.Month));

DateTime dd = new DateTime(DateTime.Now.Year, DateTime.Now.Month, 1);
            dd = (dd.DayOfWeek == DayOfWeek.Sunday) ? dd.AddDays(1) : (dd.DayOfWeek == DayOfWeek.Saturday) ? dd.AddDays(2) : dd;

            MessageBox.Show(dd.ToString());