Fürs Archiv eine kleine Funktion welche die aktuelle Kalenderwoche zurückgibt:
int NumberOfWeek()
{
CultureInfo myCultureInfo = new CultureInfo("de-DE");
Calendar myCalendar = myCultureInfo.Calendar;
CalendarWeekRule myWeeekRule = myCultureInfo.DateTimeFormat.CalendarWeekRule;
DayOfWeek myFirstDayOfWeek = myCultureInfo.DateTimeFormat.FirstDayOfWeek;
return myCalendar.GetWeekOfYear(DateTime.Now, myWeeekRule, myFirstDayOfWeek);
}