C#中通过递归获取所有的子分类

using System; using System.Collections.Generic; using System.Linq;  namespace RecursionDemo {     /// <summary>     /// 树节点     /// </summary>     public class TreeNode     {         /// <summary>         /// 节点Id         /// </summary>         public int Id { get; set; }          /// <summary>         /// 节点名称         /// </summary>         public string Name { get; set; }          /// <summary>         /// 父节点Id         /// </summary>         public int ParentId { get; set; }          /// <summary>         /// 子节点         /// </summary>         public List<TreeNode> Children { get; set; }     }      /// <summary>     /// 树节点业务逻辑     /// </summary>     public class TreeNodeBLL     {         /// <summary>         /// 通过递归获取所有子孙节点         /// </summary>         /// <param name="parentId">父节点Id</param>         /// <param name="listAllTreeNode">所有节点数据</param>         /// <returns>返回所有子孙节点</returns>         public List<TreeNode> GetChildren(int parentId, List<TreeNode> listAllTreeNode)         {             var listResult = new List<TreeNode>(); //存放返回结果的集合             var listChildren = listAllTreeNode.FindAll(node => node.ParentId == parentId);             if (listChildren.Count <= 0)             {                 //此处是返回 null 值，还是要返回 listResult ，则需要根据具体的业务逻辑来决定                 return null; //return listResult;             }              //遍历指定parentId下的第一级子节点             foreach (var item in listChildren)             {                 var childNode = new TreeNode();                 childNode.Id = item.Id;                 childNode.Name = item.Name;                 childNode.ParentId = item.ParentId;                 childNode.Children = GetChildren(item.Id, listAllTreeNode); //递归获取子节点下的子节点                 listResult.Add(childNode);             }              return listResult;         }          /// <summary>         /// 初始化级联数据（用于演示）         /// </summary>         /// <returns></returns>         public List<TreeNode> InitData()         {             //级联数据，此处以省市区级联数据为例             var listAllTreeNode = new List<TreeNode>() {                 new TreeNode() {                     Id = 1,                     ParentId = 0,                     Name = "福建省"                 },                 new TreeNode() {                     Id = 2,                     ParentId = 0,                     Name = "上海市"                 },                 new TreeNode()                 {                     Id = 3,                     ParentId = 1,                     Name = "福州市"                 },                 new TreeNode()                 {                     Id = 4,                     ParentId = 1,                     Name = "厦门市"                 },                 new TreeNode()                 {                     Id = 5,                     ParentId = 3,                     Name = "永泰县"                 },                 new TreeNode()                 {                     Id = 6,                     ParentId = 2,                     Name = "黄浦"                 },                 new TreeNode()                 {                     Id = 7,                     ParentId = 2,                     Name = "虹口"                 },                 new TreeNode()                 {                     Id = 8,                     ParentId = 2,                     Name = "宝山"                 }             };             return listAllTreeNode;         }     } }

using Newtonsoft.Json;  namespace RecursionDemo {     /// <summary>     /// 递归Demo     /// </summary>     internal class Program     {         static void Main(string[] args)         {             //示例1：C#中通过递归获取所有的子分类             var treeNodeBLL = new TreeNodeBLL();             var listAllTreeNode = treeNodeBLL.InitData();             var childrenNode = treeNodeBLL.GetChildren(0, listAllTreeNode);             var childrenNodeJson = JsonConvert.SerializeObject(childrenNode); //序列化成Json字符串             Console.WriteLine(childrenNodeJson);              //换行             Console.WriteLine();              //示例2：求 斐波那契数列 第n项是多少？（通过递归方式获取）             int n = 8; //第8项             int result = GetFibonacciSequence(n);             Console.WriteLine(string.Format(@"斐波那契数列 第{0}项是：{1}", n, result));             Console.ReadKey();         }          /// <summary>         /// 获取 斐波那契数列 第n项的值 （通过递归方式获取）         /// </summary>         /// <param name="n">第n项</param>         /// <returns>第n项的值</returns>         static int GetFibonacciSequence(int n)         {             //斐波那契数列指的是这样一个数列：1，1，2，3，5，8，13，21，34，55，89...             //这个数列从第3项开始，每一项都等于前两项之和。             if (n < 3)             {                 return 1;             }              return GetFibonacciSequence(n - 1) + GetFibonacciSequence(n - 2); //通过递归获取前两项之和         }     } }

[     {         "Id":1,         "Name":"福建省",         "ParentId":0,         "Children":[             {                 "Id":3,                 "Name":"福州市",                 "ParentId":1,                 "Children":[                     {                         "Id":5,                         "Name":"永泰县",                         "ParentId":3,                         "Children":null                     }                 ]             },             {                 "Id":4,                 "Name":"厦门市",                 "ParentId":1,                 "Children":null             }         ]     },     {         "Id":2,         "Name":"上海市",         "ParentId":0,         "Children":[             {                 "Id":6,                 "Name":"黄浦",                 "ParentId":2,                 "Children":null             },             {                 "Id":7,                 "Name":"虹口",                 "ParentId":2,                 "Children":null             },             {                 "Id":8,                 "Name":"宝山",                 "ParentId":2,                 "Children":null             }         ]     } ]

链接：https://pan.baidu.com/s/16PpxARzJbwNUeU26hJi0MA  提取码：sezs