C#根据Id和ParentId生成树

数据如下：

List<Node> nodes = new List<Node>();
nodes.Add(new Node() { Id = 1, Name = "中国", ParentId = 0 });
nodes.Add(new Node() { Id = 2, Name = "浙江省", ParentId = 1 });
nodes.Add(new Node() { Id = 3, Name = "杭州市", ParentId = 2 });
nodes.Add(new Node() { Id = 4, Name = "湖州市", ParentId = 2 });
nodes.Add(new Node() { Id = 5, Name = "拱墅区", ParentId = 3 });
nodes.Add(new Node() { Id = 6, Name = "西湖区", ParentId = 3 });
nodes.Add(new Node() { Id = 7, Name = "滨江区", ParentId = 3 });
nodes.Add(new Node() { Id = 8, Name = "吴兴区", ParentId = 4 });
nodes.Add(new Node() { Id = 9, Name = "南浔区", ParentId = 4 });
nodes.Add(new Node() { Id = 10, Name = "长兴县", ParentId = 4 });

现在需要根据Id和ParentId的从属关系生成一棵JSON树，以便供前端表格控件调用，树结构如下所示：

[
  {
    "Children": [
      {
        "Children": [
          {
            "Children": [
              {
                "Children": [],
                "Id": 5,
                "ParentId": 3,
                "Name": "拱墅区"
              },
              {
                "Children": [],
                "Id": 6,
                "ParentId": 3,
                "Name": "西湖区"
              },
              {
                "Children": [],
                "Id": 7,
                "ParentId": 3,
                "Name": "滨江区"
              }
            ],
            "Id": 3,
            "ParentId": 2,
            "Name": "杭州市"
          },
          {
            "Children": [
              {
                "Children": [],
                "Id": 8,
                "ParentId": 4,
                "Name": "吴兴区"
              },
              {
                "Children": [],
                "Id": 9,
                "ParentId": 4,
                "Name": "南浔区"
              },
              {
                "Children": [],
                "Id": 10,
                "ParentId": 4,
                "Name": "长兴县"
              }
            ],
            "Id": 4,
            "ParentId": 2,
            "Name": "湖州市"
          }
        ],
        "Id": 2,
        "ParentId": 1,
        "Name": "浙江省"
      }
    ],
    "Id": 1,
    "ParentId": 0,
    "Name": "中国"
  }
]

代码如下所示：

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Node> nodes = new List<Node>();
            nodes.Add(new Node() { Id = 1, Name = "中国", ParentId = 0 });
            nodes.Add(new Node() { Id = 2, Name = "浙江省", ParentId = 1 });
            nodes.Add(new Node() { Id = 3, Name = "杭州市", ParentId = 2 });
            nodes.Add(new Node() { Id = 4, Name = "湖州市", ParentId = 2 });
            nodes.Add(new Node() { Id = 5, Name = "拱墅区", ParentId = 3 });
            nodes.Add(new Node() { Id = 6, Name = "西湖区", ParentId = 3 });
            nodes.Add(new Node() { Id = 7, Name = "滨江区", ParentId = 3 });
            nodes.Add(new Node() { Id = 8, Name = "吴兴区", ParentId = 4 });
            nodes.Add(new Node() { Id = 9, Name = "南浔区", ParentId = 4 });
            nodes.Add(new Node() { Id = 10, Name = "长兴县", ParentId = 4 });

            List<Node> list = CreateTreeNodes(nodes);
            Console.WriteLine(JsonConvert.SerializeObject(list, Formatting.Indented));
            Console.ReadKey(true);
        }

        // 生成树
        static List<Node> CreateTreeNodes(List<Node> nodes)
        {
            List<Node> root = nodes.FindAll(node => node.ParentId == 0);
            return SortNodes(nodes, root);
        }

        // 递归分组
        static List<Node> SortNodes(List<Node> nodes, List<Node> root)
        {
            for (int i = 0; i < root.Count; i++)
            {
                List<Node> children = nodes.FindAll(node => node.ParentId == root[i].Id);
                SortNodes(nodes, children);
                root[i].Children = children;
            }
            return root;
        }
    }

    public class Node
    {
        /// <summary>
        /// 编号
        /// </summary>
        public int Id { get; set; }

        /// <summary>
        /// 上一级编号
        /// </summary>
        public int ParentId { get; set; }

        /// <summary>
        /// 名称
        /// </summary>
        public string Name { get; set; }

        /// <summary>
        /// 子节点
        /// </summary>
        public List<Node> Children;
    }
}