System.Globalization.Calendar.GetWeekOfYear C# (CSharp) Method

        public virtual int GetWeekOfYear(DateTime time, CalendarWeekRule rule, DayOfWeek firstDayOfWeek)
        {
            if ((int)firstDayOfWeek < 0 || (int)firstDayOfWeek > 6) {
                throw new ArgumentOutOfRangeException(
                    "firstDayOfWeek", String.Format(CultureInfo.CurrentCulture, Environment.GetResourceString("ArgumentOutOfRange_Range"),
                    DayOfWeek.Sunday, DayOfWeek.Saturday));
            }
            switch (rule) {
                case CalendarWeekRule.FirstDay:
                    return (GetFirstDayWeekOfYear(time, (int)firstDayOfWeek));
                case CalendarWeekRule.FirstFullWeek:
                    return (GetWeekOfYearFullDays(time, rule, (int)firstDayOfWeek, 7));
                case CalendarWeekRule.FirstFourDayWeek:
                    return (GetWeekOfYearFullDays(time, rule, (int)firstDayOfWeek, 4));
            }
            throw new ArgumentOutOfRangeException(
                "rule", String.Format(CultureInfo.CurrentCulture, Environment.GetResourceString("ArgumentOutOfRange_Range"),
                CalendarWeekRule.FirstDay, CalendarWeekRule.FirstFourDayWeek));

        }

        private void setDateTime()
        {
            dpTime.SelectedDate = DateTime.Now;
            dynamic setTime = dpTime.SelectedDate;

            tbWeek.Text = "Week " + cal.GetWeekOfYear(setTime, dfi.CalendarWeekRule, dfi.FirstDayOfWeek);
        }