如何将树结构数据从数据库序列化为 JSON

Question

我的数据存储中有一个表示树结构的数据。以下代码表示如何在 C# 中的简单 DataTable 中对其进行描述。

using System.Data;

namespace DemoConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            DataTable treeData = new DataTable();
            treeData.Clear();
            treeData.Columns.Add("NodeId", typeof(int));
            treeData.Columns.Add("ParentNodeId", typeof(int));
            treeData.Columns.Add("Data", typeof(string));
            treeData.Columns.Add("AbsolutePath", typeof(string));

            DataRow record1 = treeData.NewRow();
            record1["NodeId"] = 1;
            record1["ParentNodeId"] = 0;
            record1["Data"] = "Dairy";
            record1["AbsolutePath"] = "/Dairy/";
            treeData.Rows.Add(record1);

            DataRow record2 = treeData.NewRow();
            record2["NodeId"] = 2;
            record2["ParentNodeId"] = 1;
            record2["Data"] = "Yoghurt";
            record2["AbsolutePath"] = "/Dairy/Yoghurt";
            treeData.Rows.Add(record2);

            DataRow record3 = treeData.NewRow();
            record3["NodeId"] = 3;
            record3["ParentNodeId"] = 1;
            record3["Data"] = "Cheese";
            record3["AbsolutePath"] = "/Dairy/Cheese";
            treeData.Rows.Add(record3);

            DataRow record4 = treeData.NewRow();
            record4["NodeId"] = 4;
            record4["ParentNodeId"] = 2;
            record4["Data"] = "Flavored";
            record4["AbsolutePath"] = "/Dairy/Yoghurt/Flavored";
            treeData.Rows.Add(record4);
        }
    }
}

我需要将数据序列化成如下结构。

{
  "TreeData": {
    "NodeId" : "1",
    "Data" : "Dairy",
    "Children": [
      {
        "NodeId": "2",
        "Data": "Yohurt",
        "Children": [
          {
              "NodeId": "4",
              "Data": "Flavored",
              "Children": []
          }
        ]
      },
      {
        "NodeId": "3",
        "Data": "Cheese",
        "Children": []
      }
    ]
  }
}

我该如何实现这一目标？

Answer 1

创建一个新类：

class Node
{
    public int NodeId;
    public int ParentNodeId;
    public string Data;
    public string AbsolutePath;
    public List<Node> Children = new List<Node>();
}

然后遍历 DataTable 的行，创建适当的树结构并简单地调用 JsonConvert.SerializeObject()

var nodes = new Dictionary<int, Node>();
foreach(DataRow record in treeData.Rows)
{
    var node = new Node { NodeId = (int)record["NodeId"], ParentNodeId = (int)record["ParentNodeId"], Data = (string)record["Data"], AbsolutePath = (string)record["AbsolutePath"] };
    nodes.Add(node.NodeId, node);
}

var rootNodeId = 1;
var rootNode = nodes[rootNodeId];
foreach(var keyValuePair in nodes)
{
    var node = keyValuePair.Value;
    if(node.NodeId != rootNodeId)
    {
        nodes[node.ParentNodeId].Children.Add(node);
    }
}

string json = JsonConvert.SerializeObject(rootNode, Formatting.Indented);
Debug.WriteLine(json);

输出：

{
  "NodeId": 1,
  "ParentNodeId": 1,
  "Data": "Dairy",
  "AbsolutePath": "/Dairy/",
  "Children": [
    {
      "NodeId": 2,
      "ParentNodeId": 1,
      "Data": "Yoghurt",
      "AbsolutePath": "/Dairy/Yoghurt",
      "Children": [
        {
          "NodeId": 4,
          "ParentNodeId": 1,
          "Data": "Flavored",
          "AbsolutePath": "/Dairy/Flavored",
          "Children": []
        }
      ]
    },
    {
      "NodeId": 3,
      "ParentNodeId": 1,
      "Data": "Cheese",
      "AbsolutePath": "/Dairy/Cheese",
      "Children": []
    }
  ]
}

Answer 2

you need to make custom recursive function with Serialization Class
which will append Children till you get leaf node.
Below is example for that. please use your logic to append JsonString
var appendJsonString;

Private string PassParentId(int Id)
{
      var childnodecount=0;
      childnodecount=getchildnode(Id);   
     while(childnodecount>0)
     {
       getchilddata=getchildnode(Id);
       childnodecount=getchilddata.count();
       appendJsonString = getchilddata();
    }
    return appendJsonString;
}

Answer 3

我的方法是创建一个对象（例如 TreeDataNode）并为该对象提供以下变量

public class TreeDataNode{
    int nodeId;
    string data;
    List<TreeDataNode> children;

    public void AddChildren(string relativePath, TreeDataNode node)
    {
        string[] path = relativePath.Split('/');
        if(path.Count<2)
        {
            children.Add(node);
        }else
        {
            string newPath = String.Join(@"/", relativePath.Split('\\').Skip(1));
            children.First(n=> n.data==path[0]).AddChildren(newPath,node);
        }
    }
}

一旦您填充了这个对象，拥有一个父 TreeDataNode 和后续的子节点，您只需使用任何标准 JSON 序列化程序对其进行序列化，您将拥有一个与您尝试实现的结构一样的结构。

现在，您只需要确保按顺序添加对象，不要在孩子之后添加父母，就可以了。使用根对象创建您的父 TreeDataNode，然后为该父对象上的每个对象调用 AddChildren。