从日期集合C#中查找日期范围

Question

简单的问题.我有一个有序的日期集合.他们是英国约会顺便说一句

01/01/10
01/02/10
01/03/10
01/04/10
02/04/10
03/04/10
04/04/10

我想将其转换为日期范围的集合

01/01/10 -> 01/01/10
01/02/10 -> 01/02/10
01/03/10 -> 01/03/10
01/04/10 -> 04/04/10

只是为了澄清,我正在尝试将任何连续日期转换为范围.因此,前3个日期是独立的,最后4个日期将转换为4月1日至4月4日的范围.

现在我可以使用循环来做到这一点,但它不是很优雅.有没有人有任何解决方案？

谢谢

Answer 1

鉴于您想要确定连续日期范围的范围,我认为您唯一的选择是,正如您所说的循环.您可以在一次通过中执行此操作,并将其放在扩展方法中,以便它可以在任何操作上运行IList<DateTime>,例如:

// purely an example, chances are this will have actual, y'know logic in live
public class DateRange
{
    private List<DateTime> dates = new List<DateTime>();

    public void Add(DateTime date)
    {
        this.dates.Add(date);
    }

    public IEnumerable<DateTime> Dates
    {
        get { return this.dates; }
    }
}

public static IEnumerable<DateRange> GetRanges(this IList<DateTime> dates)
{
    List<DateRange> ranges = new List<DateRange>();
    DateRange currentRange = null;

    // this presumes a list of dates ordered by day, if not then the list will need sorting first
    for( int i = 0; i < dates.Count; ++i )
    {
        var currentDate = dates[i];
        if( i == 0 || dates[i - 1] != currentDate.AddDays(-1))
        {
            // it's either the first date or the current date isn't consecutive to the previous so a new range is needed
            currentRange = new DateRange();
            ranges.Add(currentRange);
        }

        currentRange.Add(currentDate);
    }

    return ranges;
}

您还可以通过传入以下内容使其更加通用IEnumerable<DateTime>:

public static IEnumerable<DateRange> GetRanges(this IEnumerable<DateTime> dates)
{
    List<DateRange> ranges = new List<DateRange>();
    DateRange currentRange = null;
    DateTime? previousDate = null;

    // this presumes a list of dates ordered by day, if not then the list will need sorting first
    foreach( var currentDate in dates )
    {
        if( previousDate == null || previousDate.Value != currentDate.AddDays(-1) )
        {
            // it's either the first date or the current date isn't consecutive to the previous so a new range is needed
            currentRange = new DateRange();
            ranges.Add(currentRange);
        }

        currentRange.Add(currentDate);
        previousDate = currentDate;
    }

    return ranges;
}