Check out example codes for "get what week of the month c#". It will help you in understanding the concepts better.

Code Example 1

static int GetWeekNumberOfMonth(DateTime date)
{
    date = date.Date;
    DateTime firstMonthDay = new DateTime(date.Year, date.Month, 1);
    DateTime firstMonthMonday = firstMonthDay.AddDays((DayOfWeek.Monday + 7 - firstMonthDay.DayOfWeek) % 7);
    if (firstMonthMonday > date)
    {
        firstMonthDay = firstMonthDay.AddMonths(-1);
        firstMonthMonday = firstMonthDay.AddDays((DayOfWeek.Monday + 7 - firstMonthDay.DayOfWeek) % 7);
    }
    return (date - firstMonthMonday).Days / 7 + 1;
}

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