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Accepted
iiKuzmychov
Asked:2022-04-04 07:14:23 +0800 CST2022-04-04 07:14:23 +0800 CST

如何从一个 C# 形成另一个字典

  • 772

我有一个项目字典，Dictionary<string, Dictionary<DateTime, NZMark>> subjectsDatesMarks其中存储了带有成绩的日期列表。

我怎样才能把它变成以下形式：Dictionary<DateTime, Dictionary<string, NZMark>> datesSubjectsMarks？

public enum NZMark
{
    One = 1,
    Two,
    Three,
    Four,
    Five,
    Six,
    Seven,
    Eight,
    Nine,
    Ten,
    Eleven,
    Twelve,
    WasAbsent,
    NotCertified,
    Exempted,
    Studied
}

最小的可重现示例：

var subjectsDatesMarks = new Dictionary<string, Dictionary<DateTime, NZMark>>();

subjectsDatesMarks.Add("math", new Dictionary<DateTime, NZMark>());
subjectsDatesMarks["math"].Add(new DateTime(2021, 03, 20), (NZMark)8);
subjectsDatesMarks["math"].Add(new DateTime(2021, 03, 21), (NZMark)8);
subjectsDatesMarks["math"].Add(new DateTime(2021, 03, 22), (NZMark)10);

subjectsDatesMarks.Add("PE", new Dictionary<DateTime, NZMark>());
subjectsDatesMarks["PE"].Add(new DateTime(2021, 03, 20), (NZMark)10);
subjectsDatesMarks["PE"].Add(new DateTime(2021, 03, 21), (NZMark)11);
subjectsDatesMarks["PE"].Add(new DateTime(2021, 03, 22), (NZMark)10);

var datesSubjectsMarks = MagickTransform(subjectsDatesMarks); // та самая функция для преобразования, которая мне нужна
var mathMark2021_03_22 = datesSubjectsMarks[new DateTime(2021, 03, 22)]["math"]; // 10
c#

1 个回答

  1. Best Answer

    好吧，例如像这样：

    Dictionary<DateTime, Dictionary<string, NZMark>> datesSubjectsMarks =
    subjectsDatesMarks.SelectMany(e => e.Value.Select(dtmark => (subj: e.Key,
                                                                 dt: dtmark.Key,
                                                                 mark: dtmark.Value)))
                      .GroupBy(triple => triple.dt)
                      .ToDictionary(g => g.Key,
                                    g => g.ToDictionary(triple => triple.subj,
                                                        triple => triple.mark));

    检查。

    查询语法的另一个选项：

    Dictionary<DateTime, Dictionary<string, NZMark>> datesSubjectsMarks =
   (from kvp in subjectsDatesMarks
    let subj = kvp.Key
    from dtmark in kvp.Value
    let dt = dtmark.Key
    let mark = dtmark.Value
    group (subj, mark) by dt)
   .ToDictionary(g => g.Key,
                 g => g.ToDictionary(v => v.subj, v => v.mark));
    • 7

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