c# 递归树型结构

 /// <summary>
        /// 分类树形结构  http://192.168.2.177:1222/api/classification/GetclassificationTree
        /// </summary>
        /// <returns></returns>
        [Route("api/classification/GetclassificationTree")]
        [HttpGet]
        public string GetclassificationTree()
        {
         
            WebApplication.Controllers.TreeMethod tm = new TreeMethod();

            // 找到所有的父节点  
            List<TreeEntity> treeList1 = tm.findAllParents();

            if (treeList1 != null)
            {
               
                for (int i = 0; i < treeList1.Count; i++)
                {
                   
                    TreeEntity tree = treeList1[i];
                    // 拼接父节点  
                    //result += "|--" + tree.name;
                    result += "{id:"+tree.id+ ",pId:"+tree.pid+",name:'"+tree.name+"'},";
                    // 绑定孩子  
                    ChildResult = tm.BindChildByParent(tree.id, "").TrimEnd(',');
                    temp = result + ChildResult;
                }
               
            }
            else
            {
                temp += "没有数据！";
            }
            result = "["+ temp.TrimEnd(',')+ "]";
            return SqlSugar.JsonConverter.Serialize(new { Result = 1, Msg = "获取数据成功",Data= temp });
        }
    }
    public class TreeEntity
    {
        public string id { get; set; }
        public string name { get; set; }
        public string pid { get; set; }
    }
    internal class TreeMethod
    {
        /// <summary>
        /// 找到所有的父节点
        /// </summary>
        /// <returns></returns>
        public List<TreeEntity> findAllParents()
        {
            List<TreeEntity> treeList = new List<TreeEntity>();

            using (var db = SugarDao.GetInstance())
            {
                var list = db.Queryable<tb_classification>().Where(it => it.pid == 0 && it.status==1).ToList();
                if (list.Count > 0)
                {
                    for (int i = 0; i < list.Count; i++)
                    {
                        TreeEntity myTree = new TreeEntity();
                        myTree.id = list[i].id.ToString();
                        myTree.name = list[i].title;
                        myTree.pid = list[i].pid.ToString();
                        treeList.Add(myTree);
                    }
                }
            }
            return treeList;
        }

        /// <summary>
        /// 根据父节点找到所有的子节点
        /// </summary>
        /// <param name="pid"></param>
        /// <returns></returns>
        public List<TreeEntity> findChildByPid(string pid)
        {
            int p_id = Convert.ToInt32(pid);
            List<TreeEntity> treeList = new List<TreeEntity>();

            using (var db = SugarDao.GetInstance())
            {
                var list = db.Queryable<tb_classification>().Where(it => it.pid == p_id&&it.status==1).ToList();
                if (list.Count > 0)
                {
                    for (int i = 0; i < list.Count; i++)
                    {
                        TreeEntity myTree = new TreeEntity();
                        myTree.id = list[i].id.ToString();
                        myTree.name = list[i].title;
                        myTree.pid = list[i].pid.ToString();
                        treeList.Add(myTree);
                    }
                }
            }
            return treeList;
        }
        /// <summary>
        /// 查看是否存在子节点
        /// </summary>
        /// <param name="pid"></param>
        /// <returns></returns>
        public bool HasChild(string pid)
        {
            int p_id = Convert.ToInt32(pid);
            int count = 0;
            bool flag = false;
            using (var db = SugarDao.GetInstance())
            {
                var list = db.Queryable<tb_classification>().Where(it => it.pid == p_id&it.status==1).ToList();

                for (int i = 0; i < list.Count; i++)
                {
                    count++;
                }
                if (count > 0)
                {
                    flag = true;
                }
            }
            return flag;
        }
        string Tree = string.Empty;
        /// <summary>
        /// 使用递归拼接父节点的子节点
        /// </summary>
        /// <param name="pid"></param>
        /// <param name="prefix"></param>
        public string BindChildByParent(string pid, string prefix)
        {
           
            if (this.HasChild(pid))
            {
                // 得到当前父节点下的所有孩子  
                List<TreeEntity> list = this.findChildByPid(pid);
                // 循环拼接当前父节点下的孩子  
                for (int i = 0; i < list.Count; i++)
                {
                    //Tree += "|----" + prefix + list[i].name;
                    Tree += "{id:" + list[i].id + ",pId:" + list[i].pid + ",name:'" + list[i].name + "'},";
                    if (this.HasChild(list[i].id))
                    {
                        this.BindChildByParent(list[i].id, "--");
                    }
                }
            }
            return Tree;
        }
    }

最终效果：

"{\"Result\":1,\"Msg\":\"获取数据成功\",\"Data\":\"{id:1,pId:0,name:\\u0027新闻\\u0027},{id:16,pId:0,name:\\u0027蔬菜\\u0027},{id:2,pId:1,name:\\u0027娱乐新闻\\u0027},{id:20,pId:2,name:\\u0027新增新闻分类\\u0027},{id:23,pId:20,name:\\u0027新增新闻分类2\\u0027},{id:26,pId:23,name:\\u0027新增分类3\\u0027},{id:7,pId:1,name:\\u0027时政新闻\\u0027},{id:8,pId:1,name:\\u0027科教文卫\\u0027},{id:9,pId:1,name:\\u0027城建公交\\u0027},{id:10,pId:1,name:\\u0027经济新闻\\u0027},{id:11,pId:1,name:\\u0027政法新闻\\u0027},{id:12,pId:1,name:\\u0027社会新闻\\u0027},{id:13,pId:1,name:\\u0027体育新闻\\u0027},{id:14,pId:1,name:\\u0027军事新闻\\u0027},{id:15,pId:1,name:\\u0027国际新闻\\u0027},{id:18,pId:16,name:\\u0027白菜\\u0027},{id:19,pId:16,name:\\u0027萝卜\\u0027},\"}"