How to get week number from the Date in C#

To get the week number from the Date in C#, use following function

public static int GetWeekNumber(DateTime thisDate)
    {
        return CultureInfo.InvariantCulture.Calendar.GetWeekOfYear(thisDate, System.Globalization.CalendarWeekRule.FirstDay, DayOfWeek.Sunday);
    }

This returns week number assuming first day of the week is Sunday.