Question

所以我拥有所有这些旅行日期，从日期到目前为止。我想把所有的旅行日加起来，然后按年份排序。但是，如果一次旅行超过两年，我的代码将达到错误的总和:-(

鉴于

From date   To date      Number of days
01.01.2001  01.02.2001   32
01.01.2002  01.02.2002   32
01.05.2002  01.08.2002   93
20.12.2002  01.03.2003   72
01.02.2009  01.02.2010   366
01.01.2013  02.02.2015   763

                   Sum   1358

我的代码生成了这个。但是，它犯了一个错误：

Year    Total days
2001    32
2002    137
2003    60
2009    334
2010    32
2013    365
2014    398        <---- here is a case where my code is wrong

Sum     1358

代码

var dates = new Dictionary<int, int>();
var stays = GetStays();
var returnString = "Year, Total days<br><br>";
foreach (var stay in stays)
{
    var totalTravelDays = stay.ToDate.Value.AddDays(1) - stay.FromDate;

    var currentYear = stay.FromDate.Value.Year;
    var nextYear = stay.FromDate.Value.AddYears(1).Year;
    var nextYearDate = new DateTime(stay.FromDate.Value.Year, 1, 1).AddYears(1);

    var daysInThisYear = new TimeSpan?();
    var daysInNextYear = new TimeSpan?();

    if (stay.FromDate.Value.Year != stay.ToDate.Value.Year)
    {
        daysInThisYear = nextYearDate - stay.FromDate;
        daysInNextYear = totalTravelDays - daysInThisYear;
    }
    else
    {
        daysInThisYear = totalTravelDays;
        daysInNextYear = new TimeSpan(0);
    }

    if (dates.ContainsKey(currentYear))
        dates[currentYear] += daysInThisYear.Value.Days;
    else
        dates[currentYear] = daysInThisYear.Value.Days;

    if (dates.ContainsKey(nextYear))
        dates[nextYear] += daysInNextYear.Value.Days;
    else
        dates[nextYear] = daysInNextYear.Value.Days;
}

帮助赞赏：）

Answer 1

假设var stays = List<Stay>();，你可以试试这个：

var days = stays.SelectMany(s =>
        Enumerable
            .Range(0, (s.ToDate - s.FromDate).Days + 1)
            .Select(d => s.FromDate.AddDays(d)))
    .GroupBy(d => d.Year)
    .Select(s => new { Year = s.Key, TotalDays = s.Count() })
    .ToList();

days.ForEach(d =>
{
    Console.WriteLine("{0} {1}", d.Year, d.TotalDays);
});

以上的输出是：

Answer 2

如果您编写辅助方法将日期范围拆分为按年划分的多个范围：

IEnumerable<Tuple<DateTime,DateTime>> 
    SplitDateRangeByYear(DateTime fromDate, DateTime toDate)
{
    var start = fromDate;
    for(var y = fromDate.Year; y < toDate.Year; ++y)
    {
        var nextYear = y + 1;
        var nextYearStartDate = new DateTime(nextYear, 1, 1);
        yield return Tuple.Create(start, nextYearStartDate);
        start = nextYearStartDate;
    }
    yield return Tuple.Create(start, toDate);
}

然后你可以写一些方便的Linq来做你的出价：

    var yearlyTotals = stays
        .SelectMany(s => SplitDateRangeByYear(s.FromDate, s.ToDate))
        .GroupBy(x => x.Item1.Year)
        .Select(g => new{
                Year = g.Key, 
                NumDays= g.Sum(x => (x.Item2 - x.Item1).TotalDays)});

这是您要求的更通用的解决方案，因为它将正确处理子日TimeSpan组件（即您的范围包括一天中的时间）。

Answer 3

您不需要如此大的代码来计算两个日期之间的天数;你可以依靠更简单/更准确的方法。例如：

DateTime date1 = new DateTime(2013, 1, 1);
DateTime date2 = new DateTime(2015, 2, 2);

int totDays = Math.Abs(date1.Subtract(date2).Days);

适应您的具体情况：

int[] days = new int[Math.Abs(date1.Year - date2.Year) + 1];
int curYear = 0;
if (date1.Year != date2.Year)
{
    if(date1.Year > date2.Year)
    {
        DateTime temp = date1;
        date1 = date2;
        date2 = temp;
    }
    int curYearNo = date1.Year - 1;
    curYear = -1;
    do
    {
        curYearNo = curYearNo + 1;
        curYear = curYear + 1;
        if (curYearNo < date2.Year)
        {
            days[curYear] = Math.Abs(new DateTime(curYearNo, 1, 1).Subtract(new DateTime(curYearNo, 12, 31)).Days) + 1; //Without +1 it would output 364/365 (because of not including both 1st January and 31st December)
        }
        else
        {
            days[curYear] = Math.Abs(new DateTime(curYearNo, 1, 1).Subtract(date2).Days);
        }
    } while (curYearNo < date2.Year);
}
else
{
    days[curYear] = Math.Abs(date1.Subtract(date2).Days);
}

时间差的总和差异，按每年的旅行天数排序

3 个答案: