asp.net    

首先、根据年和月算月份的天数函数

       private int GetDayNumber(int year, int month)
        {
            int[] days = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
            if (2 == month && 0 == (year % 4) && (0 != (year % 100) || 0 == (year % 100)))
                days[1] = 29;
            return days[month - 1];
        }

其次、调用

  int  DayNumbe=  GetDayNumber(int year, int month)