calulate month from week no

Question

i am getting week no from database need to calculate which week of the month it is.

for ex:

week no = 7 month = 2

week no 11 month = 3

How to calculate it??

Just to add on i also have the year value with the week no.

Answer 1

Ok, I'll have a go, but it's not very pretty:

public int MonthOfWeek( int week, int year, CalendarWeekRule, weekrule, DayOfWeek firstDayOfWeek)
{
  GregorianCalendar gc = new GregorianCalendar();
  for( DateTime dt = new DateTime(year, 1, 1); dt.Year == year; dt = dt.AddDays(1))
  {
    if( gc.GetWeekOfYear( dt, System.Globalization.CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday) == week ){
      return dt.Month;
    }
  }
  return -1;
}  

This takes into consideration the culture specific rules for generating weeks. If a week is split between two months it will return the first month it encounters.

So in Norway, I would call this with CalendarWeekRule.FirstFourDayWeek and DayOfWeek.Monday for correct results.