转换日期列表以便在包含连续天数的情况下按组显示的最佳方法是什么?

Question

我有一个日期列表

 var list = new List<DateTime>();
 list.Add(new DateTime(2014, 1,1);
 list.Add(new DateTime(2014, 1,2);
 list.Add(new DateTime(2014, 1,3);
 list.Add(new DateTime(2014, 1,5);
 list.Add(new DateTime(2014, 1,6);
 list.Add(new DateTime(2014, 1,11);

和某些日期是连续的。我想把连续的日期组合在一起，并在UI上渲染为:

"Jan 1-3, 2015; Jan 5-6, 2015; Jan 11, 2015"

什么是正确的方法来做这个列表转换?没有这个。我会这样做:

 var display = String.Join(";", list.Select(r=>r.ToString("dd-MMM-yyyy"));

Answer 1

void Main()
{
    var list = new List<DateTime>();
    list.Add(new DateTime(2014, 1, 1));
    list.Add(new DateTime(2014, 1, 2));
    list.Add(new DateTime(2014, 1, 3));
    list.Add(new DateTime(2014, 1, 5));
    list.Add(new DateTime(2014, 1, 6));
    list.Add(new DateTime(2014, 1, 11));
    string output = string.Join("; ", GetRanges(list).Select(FormatRange));
    Console.WriteLine(output);
    // Jan 1–3, 2014; Jan 5–6, 2014; Jan 11, 2014
}
private string FormatRange (DateRange range)
{
    if (range.Start.Year != range.End.Year)
        return range.Start.ToString("MMM d, yyyy") + " – " + range.End.ToString("MMM d, yyyy");
    else if (range.Start.Month != range.End.Month)
        return range.Start.ToString("MMM d") + " – " + range.End.ToString("MMM d, yyyy");
    else if (range.Start.Day != range.End.Day)
        return range.Start.ToString("MMM d") + "–" + range.End.ToString("d, yyyy");
    else
        return range.Start.ToString("MMM d, yyyy");
}
private List<DateRange> GetRanges (IEnumerable<DateTime> dates)
{
    List<DateRange> ranges = new List<DateRange>();
    DateRange current = null;
    DateTime? previous = null;
    foreach (DateTime date in dates)
    {
        if (!previous.HasValue)
            current = new DateRange() { Start = date };
        else if ((date - previous.Value).Days > 1)
        {
            current.End = previous.Value;
            ranges.Add(current);
            current = new DateRange() { Start = date };
        }   
        previous = date;
    }
    if (previous.HasValue)
    {
        current.End = previous.Value;
        ranges.Add(current);
    }
    return ranges;
}
public class DateRange
{
    public DateTime Start { get; set; }
    public DateTime End { get; set; }
}

Answer 2

这将完成工作:

    private string BuildRanges(List<DateTime> DateList)
    {
        string result = "";
        int start = 0;
        int end = 0;
        DateTime curr, prev;
        for (int i = 1; i <= DateList.Count; i++)
        {
            if (i < DateList.Count)
            {
                curr = DateList[i];
                prev = DateList[i - 1];
                if (curr.Year == prev.Year && curr.Month == prev.Month && curr.Day == prev.Day + 1)
                {
                    end = i;
                    continue;
                }
            }
            if (start == end)
            {
                result += DateList[start].ToString("MMM d, yyyy");
            }
            else
            {
                result += DateList[start].ToString("MMM d") + "-" + DateList[end].ToString("d, yyyy");
            }
            result += "; ";
            start = end = i;
        }
        return result.Substring(0, result.Length - 2);
    }

像这样使用:

        var list = new List<DateTime>();
        list.Add(new DateTime(2014, 1, 1));
        list.Add(new DateTime(2014, 1, 2));
        list.Add(new DateTime(2014, 1, 3));
        list.Add(new DateTime(2014, 1, 5));
        list.Add(new DateTime(2014, 1, 6));
        list.Add(new DateTime(2014, 1, 11));
        var display = BuildRanges(list);