给定从日期中减去的工作日小时数，是否有更好的方法来计算新日期？

Question

给定日期和小时数，如果我仅使用工作日时间（没有周末时间（没有周六或周日时间））减去小时数，我想计算一个新日期。

在减去工作日时间时，我有以下两个函数来计算日期。有没有更好的办法？

static DateTime SubtractWeekdayHours
    (
        DateTime date2subtractFrom
        , int hours2subtract
    )
    {
        if (hours2subtract < 1 || hours2subtract > 120)
            throw new Exception("SubtractWeekdayHours() only subtracts hours between 1 and 120 inclusive.");

        var weekdayDateTime = DateTime.Now;

        //  Check if the end of the span touches the weekend:
        if (date2subtractFrom.DayOfWeek == DayOfWeek.Saturday || date2subtractFrom.DayOfWeek == DayOfWeek.Sunday)
        {
            Debug.Write(", End of span EXCEPTION: " + date2subtractFrom.ToString("F"));
            var SaturdayStartOf = date2subtractFrom.DayOfWeek == DayOfWeek.Saturday ? date2subtractFrom.Date : date2subtractFrom.AddDays(-1).Date;
            weekdayDateTime = SaturdayStartOf.AddHours(-hours2subtract);
        }
        else
        {   //  Check if the start of the span touches the weekend:
            var possibleWeekendDate = date2subtractFrom.AddHours(-hours2subtract);
            if (possibleWeekendDate.DayOfWeek == DayOfWeek.Saturday || possibleWeekendDate.DayOfWeek == DayOfWeek.Sunday)
            {
                Debug.Write(", Start of span EXCEPTION: " + possibleWeekendDate.ToString("F"));
                weekdayDateTime = calculateWeekdayDateTimeWhenSpanTouchesWeekend(possibleWeekendDate, date2subtractFrom, hours2subtract);
            }
            else
            {
                var simpleSubtraction = false;
                var daysToCheck = hours2subtract / 24;
                if (daysToCheck > 0)
                {   //  Check if any part of the span touches the weekend:
                    var weekendTouched = false;
                    for (var x = -daysToCheck; x < 0; x++)
                    {
                        possibleWeekendDate = date2subtractFrom.AddDays(x);
                        if (possibleWeekendDate.DayOfWeek == DayOfWeek.Saturday || possibleWeekendDate.DayOfWeek == DayOfWeek.Sunday)
                        {
                            weekendTouched = true;
                            Debug.Write(", Span EXCEPTION:" + possibleWeekendDate.ToString("F"));
                            weekdayDateTime = calculateWeekdayDateTimeWhenSpanTouchesWeekend(possibleWeekendDate, date2subtractFrom, hours2subtract);
                            break;
                        }
                    }

                    if (!weekendTouched)
                    {   //  Span start and end do not touch a weekend and do not span a weekend, so it is just simple subtraction:
                        simpleSubtraction = true;
                    }
                }
                else
                {   //  Span start and end do not touch a weekend and the number of hours are less than 24, so it is just simple subtraction:
                    simpleSubtraction = true;
                }

                if (simpleSubtraction)
                {
                    Debug.Write(", Simple subtraction:");
                    weekdayDateTime = date2subtractFrom.AddHours(-hours2subtract);
                }
            }
        }

        return weekdayDateTime;
    }

    private static DateTime calculateWeekdayDateTimeWhenSpanTouchesWeekend
    (
        DateTime weekendDate
        , DateTime date2subtractFrom
        , int hours2subtract
    )
    {
        var MondayStartOf = weekendDate.DayOfWeek == DayOfWeek.Saturday ? weekendDate.AddDays(2).Date : weekendDate.AddDays(1).Date;
        var timeSpan = date2subtractFrom - MondayStartOf;
        var hoursLeft = hours2subtract - timeSpan.TotalHours;
        var SaturdayStartOf = MondayStartOf.AddDays(-2);
        return SaturdayStartOf.AddHours(-hoursLeft);
    }

Answer 1

我相信这如您所描述的那样有效，但您应该对其进行一些测试。 基本上我要做的就是在一个循环中不断地从我们的开始日期减去一个小时，如果结果日期不是我们应该忽略的，减少我们的“小时”计数器直到我们达到零。

这个方法允许调用者传入DayOfWeek（天）的列表和DateTime（日期）的列表，应该被忽略。下面是反映您正在做什么的实现（忽略周末）。

static DateTime SubtractHours(DateTime startDate, int hours, 
    List<DayOfWeek> daysToIgnore = null, List<DateTime> datesToIgnore = null)
{
    if (hours < 1) throw new ArgumentOutOfRangeException(nameof(hours), 
        "hours must be a positive integer");
    if (daysToIgnore == null) daysToIgnore = new List<DayOfWeek>();
    if (datesToIgnore == null) datesToIgnore = new List<DateTime>();
    var endDate = startDate;

    do
    {
        // In this loop, we continually subtract an hour from our start date
        endDate = endDate.AddHours(-1);

        // If that does not result in a day of week or date that 
        // we should ignore, then subtract one from our hours
        if (!daysToIgnore.Any(d => d.Equals(endDate.DayOfWeek)) &&
            !datesToIgnore.Any(d => d.Date.Equals(endDate.Date)))
        {
            hours--;
        }
    } while (hours > 0);

    return endDate;
}

下面是替换您创建的方法：

static DateTime SubtractWeekdayHours(DateTime startDate, int hours)
{
    var daysOfWeekToIgnore = new List<DayOfWeek> {DayOfWeek.Saturday, DayOfWeek.Sunday};
    return SubtractHours(startDate, hours, daysOfWeekToIgnore);
}

注意：我没有添加最多 120 小时的限制，但您可以添加该部分！