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我想出了一个我认为很好的问题：如何获取指定日期格式的两个日期时间之间的每个标签。想知道是否有人有比我想出的更优雅的解决方案。（除了在编译时知道格式）或任何优化它的方法。

我正在使用它来生成一个图表，其中并非所有时间段都有一个值（因此 .GroupBy(date => date.ToString(dateFormat))导致跳过任何具有零元素的时间段）

例如：输出 2011/01/01 和 2011/03/21 之间的每个标签，日期格式为“yyyyMM” GetTimeSegmentLables(new DateTime(2011,1,1), new DateTime(2011,3,21), "yyyyMM").Dump(); 这应该还支持一种格式，例如"yyyy MM 'Month' dddd\\'\\s"

这就是我想出的：

public static List<string> GetTimeSegmentLabels(DateTime startDate, DateTime endDate, string dateFormat)
{
    DateTime incrementedDate = startDate;
    TimeSpan increment = GetSmallestUnitInDateFormat(dateFormat);

    int estimatedCount = (int)((endDate - startDate).TotalMilliseconds / increment.TotalMilliseconds + 1);
    List<string> Formats = new List<string>(estimatedCount);

    string LastFormat = "";
    while (incrementedDate < endDate)
    {
        string next = incrementedDate.ToString(dateFormat);
        if (next != LastFormat)
        {
            Formats.Add(next);
            LastFormat = next;
        }
        incrementedDate = incrementedDate.Add(increment);
    }
    if (LastFormat != endDate.ToString(dateFormat))
        Formats.Add(endDate.ToString(dateFormat));

    return Formats;
}

public static TimeSpan GetSmallestUnitInDateFormat(string dateFormat)
{
    //Remove escaped characters
    string stripped = Regex.Replace(dateFormat, "(\\\\.|'[^']+'|\"[^\"]+\")", "");

    //Check for format strings in increasing order
    if (stripped.Contains("F") || stripped.Contains("F"))
    {
        //TODO find longest [fF]+ string
    }
    if (stripped.Contains("s"))
    {
        return new TimeSpan(0, 0, 1);
    }
    if (stripped.Contains("m"))
    {
        return new TimeSpan(0, 1, 0);
    }
    if (stripped.Contains("h") || stripped.Contains("H"))
    {
        return new TimeSpan(1, 0, 0);
    }
    if (stripped.Contains("d"))
    {
        return new TimeSpan(1, 0, 0, 0);
    }
    if (stripped.Contains("M"))
    {
        //30 is the average month (365.25/12) but there is a chance it would skip Feburary...
        //So 28 should hit every month for each year, hitting one twice
        return new TimeSpan(28, 0, 0, 0);
    }
    if (stripped.Contains("y"))
    {
        return new TimeSpan(365, 0, 0, 0);
    }

    throw new ArgumentOutOfRangeException("Unable to find any supported Format Specifier");
}
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