如何确定给定日期是否是该月的第N个工作日？

Question

这是我想要做的:给定日期,星期几和整数n,确定日期是否是n该月的第几天.

例如:

• 输入1/1/2009,Monday,2 将是假的,因为1/1/2009不是第二个星期一

• 输入 11/13/2008,Thursday,2 将返回true,因为它是第二个星期四

如何改进此实施？

private bool NthDayOfMonth(DateTime date, DayOfWeek dow, int n)
{
    int d = date.Day;
    return date.DayOfWeek == dow && (d/ 7 == n || (d/ 7 == (n - 1) && d % 7 > 0));
}

Answer 1

您可以更改一周的检查,以便函数读取:

private bool NthDayOfMonth(DateTime date, DayOfWeek dow, int n){
  int d = date.Day;
  return date.DayOfWeek == dow && (d-1)/7 == (n-1);
}

除此之外,它看起来非常好,效率很高.

Answer 2

答案来自这个网站.复制/粘贴此处以防网站丢失.

public static DateTime FindTheNthSpecificWeekday(int year, int month,int nth, System.DayOfWeek day_of_the_week)
{
    // validate month value
    if(month < 1 || month > 12)
    {
        throw new ArgumentOutOfRangeException("Invalid month value.");
    }

    // validate the nth value
    if(nth < 0 || nth > 5)
    {
        throw new ArgumentOutOfRangeException("Invalid nth value.");
    }

    // start from the first day of the month
    DateTime dt = new DateTime(year, month, 1);

    // loop until we find our first match day of the week
    while(dt.DayOfWeek != day_of_the_week)
    {
        dt = dt.AddDays(1);
    }

    if(dt.Month != month)
    {
        // we skip to the next month, we throw an exception
        throw new ArgumentOutOfRangeException(string.Format("The given month has less than {0} {1}s", nth, day_of_the_week));
    }

    // Complete the gap to the nth week
    dt = dt.AddDays((nth - 1) * 7);

    return dt;
}