Question

我正在一个可以创建重复任务的任务系统上工作，在某些情况下，我需要帮助来弄清楚：

我正在使用this library来确定何时创建任务并计划在接下来的28天内花费的时间。例如，每天9点：

CronExpression expression = CronExpression.Parse("0 9 * * *");

但是阅读有关Cronos表达式的信息后，我仍然不知道如何获得一个每3周重复一次的表达式。一周中的哪几天可以，但是每隔x周我都找不到。

能帮我吗？谢谢

Answer 1

我不认为您可以按周安排cron，请参见下文：我建议将同一份工作安排在一个月的不同日期。

┌───────────── minute (0 - 59)
│ ┌───────────── hour (0 - 23)
│ │ ┌───────────── day of the month (1 - 31)
│ │ │ ┌───────────── month (1 - 12)
│ │ │ │ ┌───────────── day of the week (0 - 6) (Sunday to Saturday;
│ │ │ │ │                                   7 is also Sunday on some systems)
│ │ │ │ │
│ │ │ │ │
* * * * * command to execute

https://en.wikipedia.org/wiki/Cron

Answer 2

无法使用cron表达式执行此操作。就我而言，我需要这些事件来进行一些成本计算。这是我做的似乎运行良好的功能：

        public List<DateTime> GetOccurrencesInWeeksInterval(DateTime start, DateTime end)
    {
        var ret = new List<DateTime>();
        DateTime? lastDate = null;
        int weekInterval = _rptConfig.Interval;

        CronExpression expression = CronExpression.Parse(this.GetCronExpression()); // this would return something like "0 9 * * 1,3,5"
        var dates = expression.GetOccurrences(start, end).ToList();

        if (weekInterval == 1) {
            return dates;
        }

        if (dates.Any())
        {
            foreach (var date in dates)
            {
                if (lastDate == null)
                {
                    ret.Add(date);
                    lastDate = date;
                }
                else
                {
                    var weekDiff = HelperFunctions.GetWeekDiff(lastDate.Value, date);
                    if (weekDiff == 0)
                    {
                        ret.Add(date);
                    }
                    else if (weekDiff > 0 && (weekDiff % weekInterval) == 0)
                    {
                        ret.Add(date);
                    }
                }
            }
        }

        return ret;
    }

这是GetWeekDiff函数：

        /// <summary>
    /// https://stackoverflow.com/questions/49924085/week-difference-between-2-dates-in-c-sharp#49924454
    /// </summary>
    /// <param name="dtStart"></param>
    /// <param name="dtEnd"></param>
    /// <returns></returns>
    public static int GetWeekDiff(DateTime dtStart, DateTime dtEnd, DayOfWeek startOfWeek = DayOfWeek.Monday) {

        //===============================================
        var diff = dtEnd.Subtract(dtStart);
        var weeks = (int)diff.Days / 7;

        // need to check if there's an extra week to count
        var remainingDays = diff.Days % 7;
        var cal = CultureInfo.InvariantCulture.Calendar;
        var d1WeekNo = cal.GetWeekOfYear(dtStart, CalendarWeekRule.FirstFullWeek, startOfWeek);
        var d1PlusRemainingWeekNo = cal.GetWeekOfYear(dtStart.AddDays(remainingDays), CalendarWeekRule.FirstFullWeek, startOfWeek);

        if (d1WeekNo != d1PlusRemainingWeekNo)
            weeks++;

        return weeks;

    }

希望这对某人有帮助，因为我意识到这是一个非常普遍的问题。

Asp.Net Core Hangfire Cronos表达每隔x周重复一次

2 个答案: