Get the first day of week from the week number

public string GetFirstDayOfWeek(int weekNum)
{
DateTime dt = new DateTime(DateTime.Now.Year, 1, 1);
int days = (weekNum) * 7;
DateTime dt1 = dt.AddDays(days);
DayOfWeek dow = dt1.DayOfWeek;
DateTime startDateOfWeek = dt1.AddDays(-(int)dow);
return startDateOfWeek.ToString("dd MMM");
}
public static string GetFirstDayOfWeek(DateTime dayInWeek)
{
CultureInfo cultureInfo = CultureInfo.CurrentCulture;
DayOfWeek firstDay = cultureInfo.DateTimeFormat.FirstDayOfWeek;
DateTime firstDayInWeek = dayInWeek.Date;
while (firstDayInWeek.DayOfWeek != firstDay)
firstDayInWeek = firstDayInWeek.AddDays(-1);
return firstDayInWeek;
}