Get week from selected monthcalendar-date

Question

I need a solution to calculate the week from the selected date. (in monthcalendar)
I tried:

DateTime dt1 = new DateTime(monthCalendar1.SelectionStart.Year, 
                            monthCalendar1.SelectionStart.Month, 
                            monthCalendar1.SelectionStart.Day);

DateTime dt2 = new DateTime(monthCalendar1.SelectionStart.Year, 
                            1, 
                            1);

System.TimeSpan varTime = dt1 - dt2;
int weeks = (varTime.Days / 7) + 1;

But start and enddays of a weeks are not correct and in some years I got 53 weeks?
what is the best way to solve this?

Answer 1

public int WeekNumber(DateTime date)
{
    CultureInfo ciCurr = CultureInfo.CurrentCulture;
    int weekNum = ciCurr.Calendar.GetWeekOfYear(date,
                                          CalendarWeekRule.FirstFourDayWeek,
                                          DayOfWeek.Monday);
    return weekNum;
}

Remember to correct the CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday to your current culture, the one use here is for danish/denmark