c# - 我可以使用 LINQ GroupBy 更干净地执行此操作吗？

Question

在这个人为设计的示例中，它非常类似于我的现实问题，我有一个来自外部源的数据集。来自外部源的每条记录都采用以下形式:

[Classification] NVARCHAR(32),
[Rank]           INT,
[Data]           NVARCHAR(1024)

我希望构建一个对象，其中 Rank 和 Data 被修补到响应对象的单个实例中，该实例包含三个硬编码 Classification 值，按 Rank 排序。

我有一些有用的东西，但我忍不住认为它可以做得更好。这是我的:

public static void Main()
{
    IEnumerable<GroupingTestRecord> records = new List<GroupingTestRecord>
    {
        new GroupingTestRecord { Classification = "A", Rank = 1, Data = "A1" },
        new GroupingTestRecord { Classification = "A", Rank = 2, Data = "A2" },
        new GroupingTestRecord { Classification = "A", Rank = 3, Data = "A3" },
        new GroupingTestRecord { Classification = "B", Rank = 1, Data = "B1" },
        new GroupingTestRecord { Classification = "B", Rank = 2, Data = "B2" },
        new GroupingTestRecord { Classification = "B", Rank = 3, Data = "B3" },
        new GroupingTestRecord { Classification = "C", Rank = 1, Data = "C1" },
        new GroupingTestRecord { Classification = "C", Rank = 2, Data = "C2" },
        new GroupingTestRecord { Classification = "C", Rank = 3, Data = "C3" },
    };

    GroupTestResult r = new GroupTestResult
    {
        A = records.Where(i => i.Classification == "A").Select(j => new GroupTestResultItem { Rank = j.Rank, Data = j.Data, }).OrderBy(k => k.Rank),
        B = records.Where(i => i.Classification == "B").Select(j => new GroupTestResultItem { Rank = j.Rank, Data = j.Data, }).OrderBy(k => k.Rank),
        C = records.Where(i => i.Classification == "C").Select(j => new GroupTestResultItem { Rank = j.Rank, Data = j.Data, }).OrderBy(k => k.Rank),
    };

源记录DTO:

public class GroupingTestRecord
{
    public string Classification { get; set; }
    public int? Rank { get; set; }
    public string Data { get; set; }
}

目标单类:

public class GroupTestResult
{
    public IEnumerable<GroupTestResultItem> A { get; set; }
    public IEnumerable<GroupTestResultItem> B { get; set; }
    public IEnumerable<GroupTestResultItem> C { get; set; }
}

区别子类:

public class GroupTestResultItem
{
    public int? Rank { get; set; }
    public string Data { get; set; }
}

输出

{
   "A":[
      {
         "Rank":1,
         "Data":"A1"
      },
      {
         "Rank":2,
         "Data":"A2"
      },
      {
         "Rank":3,
         "Data":"A3"
      }
   ],
   "B":[
      {
         "Rank":1,
         "Data":"B1"
      },
      {
         "Rank":2,
         "Data":"B2"
      },
      {
         "Rank":3,
         "Data":"B3"
      }
   ],
   "C":[
      {
         "Rank":1,
         "Data":"C1"
      },
      {
         "Rank":2,
         "Data":"C2"
      },
      {
         "Rank":3,
         "Data":"C3"
      }
   ]
}

Fiddle

有没有更好的方法来实现我的目标？

Answer 1

相同的 JSON 输出是使用 GroupBy 实现的首先在 Classification并申请 ToDictionary结果 IGrouping<string, GroupingTestRecord>.Key

var r = records
    .GroupBy(_ => _.Classification)
    .ToDictionary(
        k => k.Key, 
        v => v.Select(j => new GroupTestResultItem { Rank = j.Rank, Data = j.Data, }).OrderBy(k => k.Rank).ToArray()
    );

var json = JsonConvert.SerializeObject(r);

Console.WriteLine(json);

应该很容易反序列化到目标单个类(例如在客户端上)

var result = JsonConvert.DeserializeObject<GroupTestResult>(json);

is it possible to get the top level result into a GroupTestResult object?

从字典中构建结果

var result = new GroupTestResult {
    A = r.ContainsKey("A") ? r["A"] : Enumerable.Empty<GroupTestResultItem>();,
    B = r.ContainsKey("B") ? r["B"] : Enumerable.Empty<GroupTestResultItem>();,
    C = r.ContainsKey("C") ? r["C"] : Enumerable.Empty<GroupTestResultItem>();,
};