從結構化數據構建 JSON 層次結構

Question

C# | .NET 4.5 | 實體框架 5

我有以 ID、ParentID、Name 的形式從 SQL 查詢返回的數據。 我想獲取該數據並將其解析為分層 JSON 字符串。 到目前為止，這似乎是一項比應有的艱巨任務。 由於我使用的是實體，因此數據作為 IEnumerable 很好地返回給我。 現在我相信我只需要某種形式的遞歸，但我不太確定從哪里開始。 任何幫助表示贊賞。

數據返回為

id   parentId    name
1    1           TopLoc
2    1           Loc1
3    1           Loc2
4    2           Loc1A

代碼是

public static string GetJsonLocationHierarchy(long locationID)
{
    using (EntitiesSettings context = new EntitiesSettings())
    {
        // IEnumerable of ID,ParentID,Name
        context.GetLocationHierarchy(locationID);
    }
}

我希望最終的結果是這樣的：

{
    "id": "1",
    "parentId": "1",
    "name": "TopLoc",
    "children": [
        {
            "id": "2",
            "parentId": "1",
            "name": "Loc1",
            "children": [
                {
                    "id": "4",
                    "parentId": "2",
                    "name": "Loc1A",
                    "children": [
                        {}
                    ]
                }
            ]
        },
        {
            "id": "3",
            "parentId": "1",
            "name": "Loc2",
            "children": [
                {}
            ]
        }
    ]
}

Answer 1

將平面表轉換為層次結構的一種方法是將所有節點放入字典中。 然后遍歷字典，對於每個節點，查找其父節點並將其添加到父節點的子節點。 從那里，您只需要找到根並將其序列化。

這是一個演示該方法的示例程序：

class Program
{
    static void Main(string[] args)
    {
        IEnumerable<Location> locations = new List<Location>
        {
            new Location { Id = 1, ParentId = 1, Name = "TopLoc" },
            new Location { Id = 2, ParentId = 1, Name = "Loc1" },
            new Location { Id = 3, ParentId = 1, Name = "Loc2" },
            new Location { Id = 4, ParentId = 2, Name = "Loc1A" },
        };

        Dictionary<int, Location> dict = locations.ToDictionary(loc => loc.Id);

        foreach (Location loc in dict.Values)
        {
            if (loc.ParentId != loc.Id)
            {
                Location parent = dict[loc.ParentId];
                parent.Children.Add(loc);
            }
        }

        Location root = dict.Values.First(loc => loc.ParentId == loc.Id);

        JsonSerializerSettings settings = new JsonSerializerSettings
        {
            ContractResolver = new CamelCasePropertyNamesContractResolver(),
            Formatting = Formatting.Indented
        };
        string json = JsonConvert.SerializeObject(root, settings);

        Console.WriteLine(json);
    }
}

class Location
{
    public Location()
    {
        Children = new List<Location>();
    }

    public int Id { get; set; }
    public int ParentId { get; set; }
    public string Name { get; set; }
    public List<Location> Children { get; set; }
}

這是輸出：

{
  "id": 1,
  "parentId": 1,
  "name": "TopLoc",
  "children": [
    {
      "id": 2,
      "parentId": 1,
      "name": "Loc1",
      "children": [
        {
          "id": 4,
          "parentId": 2,
          "name": "Loc1A",
          "children": []
        }
      ]
    },
    {
      "id": 3,
      "parentId": 1,
      "name": "Loc2",
      "children": []
    }
  ]
}