public class CalendarHelper
{
    /// <summary>
    /// Calculates start and end date of a week for a specific year.
    /// </summary>
    /// <param name="year">Year</param>
    /// <param name="week">Week number</param>
    /// <param name="startDate">Calculated start date of week</param>
    /// <param name="endDate">Calculated end date of week</param>
    public static void StartEndDateOfWeek(int year, int week, out DateTime startDate, out DateTime endDate)
    {
        // First of January
        DateTime jan1 = new DateTime(year, 1, 1);
 
        // Calculation is done according to the first day of week is monday but includes the offset,
        // so it will be correct for sunday and other first day of week.
        int daysOffset = (int)CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek - (int)jan1.DayOfWeek;
        DateTime firstMonday = jan1.AddDays(daysOffset);
 
        // Find the first week.
        int firstWeek = CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(jan1, CultureInfo.CurrentCulture.DateTimeFormat.CalendarWeekRule,
            CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek);
 
        if (firstWeek <= 1)
        {
            week -= 1;
        }
        startDate = firstMonday.AddDays(week * 7);
        endDate = startDate.AddDays(6);            
    }
}