c# - 在 ASP.NET c# 中查找十月最后一个星期日的日期

Question

你好，有什么方法可以在 ASP.NET c# 中找出十月最后一个星期日的日期我正在使用 .net 2.0

Answer 1

不需要为此运行循环:

private static DateTime GetLastWeekdayOfMonth(DateTime date, DayOfWeek day)
{
    DateTime lastDayOfMonth = new DateTime(date.Year, date.Month, 1)
        .AddMonths(1).AddDays(-1);
    int wantedDay = (int)day;
    int lastDay = (int)lastDayOfMonth.DayOfWeek;
    return lastDayOfMonth.AddDays(
        lastDay >= wantedDay ? wantedDay - lastDay : wantedDay - lastDay - 7);
}

这可以很容易地转换为扩展方法，如下所示:

public static class DateTimeExtensions
{
    public static DateTime GetLastWeekdayOfMonth(this DateTime date, DayOfWeek day)
    {
        DateTime lastDayOfMonth = new DateTime(date.Year, date.Month, 1)
            .AddMonths(1).AddDays(-1);
        int wantedDay = (int)day;
        int lastDay = (int)lastDayOfMonth.DayOfWeek;
        return lastDayOfMonth.AddDays(
            lastDay >= wantedDay ? wantedDay - lastDay : wantedDay - lastDay - 7);
    }
}

...然后可以直接从任何 DateTime 对象使用:

DayOfWeek lastSunday = DateTime.Now.GetLastWeekdayOfMonth(DayOfWeek.Sunday);

更新:修复了一个错误。