C# 非递归生成树

原文：https://www.cnblogs.com/fzz2727551894/p/5501223.html

简单测试：

代码：

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

namespace ConsoleApp1
{
    public class Class6
    {

        //https://www.cnblogs.com/fzz2727551894/p/5501223.html



        public void test1()
        {
            var dt = ExecuteDataTable($"select * from Table_1 ", null);

            List<TreeNode> tree = TreeServices.ToTree(dt);

            Console.WriteLine(tree.Count);
        }





        // 返回DataTable
        public static DataTable ExecuteDataTable(string sql, params SqlParameter[] param)
        {
            string conStr = "data source=.\\sqlexpress;initial catalog=TEST1;user id=sa;password=sa;";
            //string conStr = "data source=192.168.2.51; initial catalog=BIMManagerDb;user id=sa;password=Sql123456; ";

            DataTable dt = new DataTable();

            using (SqlConnection con = new SqlConnection(conStr))
            {
                using (SqlDataAdapter adapter = new SqlDataAdapter(sql, con))
                {
                    //添加参数
                    if (param != null)
                    {
                        adapter.SelectCommand.Parameters.AddRange(param);
                    }
                    //1.打开链接，如果连接没有打开，则它给你打开；如果打开，就算了
                    //2.去执行sql语句，读取数据库
                    //3.sqlDataReader,把读取到的数据填充到内存表中
                    adapter.Fill(dt);
                }
            }
            return dt;
        }
    }

















    public static class k1
    {
        public static bool IsEmpty(this string str)
        {
            return false;
        }
        public static bool IsEmpty(this DataTable dt)
        {
            if (dt == null)
            {
                return true;
            }
            if (dt.Rows.Count <= 0)
            {
                return true;
            }
            return false;
        }
        public static int ToInt32(this object obj)
        {
            return int.Parse(obj.ToString());
        }
        public static bool IsEmpty<T>(this List<T> list) where T : class, new()
        {
            return false;
        }
    }


    public class TreeServices
    {
        /// <summary>
        /// 以非递归的方式生成树
        /// </summary>
        /// <param name="table"></param>
        /// <returns></returns>
        public static List<TreeNode> ToTree(DataTable table)
        {
            var list = new List<TreeNode>();
            if (table.IsEmpty()) return list;
            var dic = TreeNode.FillModel(table);
            foreach (var pair in dic)
            {
                var pid = pair.Value.ParentId;
                if (pid == 0)
                {
                    list.Add(pair.Value);
                    continue;
                }
                if (dic.ContainsKey(pid))
                {
                    dic[pid].Children.Add(pair.Value);
                }
            }
            return list;
        }
    }

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

        /// <summary>
        /// 自增Id
        /// </summary>
        public int NodeId { get; set; }

        /// <summary>
        /// 关联Id，形式1-2-3-4（该节点上一节点为4，再上一级为3，...）
        /// </summary>
        public string RelationId { get; set; }

        /// <summary>
        /// 上一个节点的Id
        /// </summary>
        public int ParentId
        {
            get
            {
                if (RelationId.IsEmpty()) return 0;
                var s = RelationId.Split('-');
                return s[s.Length - 1].ToInt32();
            }
        }

        /// <summary>
        /// 是否有下一节点
        /// </summary>
        public bool HasChild
        {
            get { return Children.IsEmpty(); }
        }

        /// <summary>
        /// 子节点集合
        /// </summary>
        public List<TreeNode> Children { get; set; }

        /// <summary>
        /// DataTable To Dictionary
        /// </summary>
        /// <param name="table"></param>
        /// <returns></returns>
        public static Dictionary<int, TreeNode> FillModel(DataTable table)
        {
            var list = new Dictionary<int, TreeNode>();
            if (table == null || table.Rows.Count == 0) return list;
            foreach (DataRow row in table.Rows)
            {
                var model = new TreeNode
                {
                    NodeId = row["Id"].ToInt32(),
                    RelationId = row["RelationId"].ToString()
                };
                list.Add(model.NodeId, model);
            }
            return list;
        }
    }
}

View Code

SQL：

USE [TEST1]
GO
/****** Object:  Table [dbo].[Table_1]    Script Date: 03/11/2020 11:36:54 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Table_1](
    [Id] [int] NOT NULL,
    [RelationId] [nvarchar](max) NULL,
    [ParentId] [int] NULL,
 CONSTRAINT [PK_Table_1] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
GO
INSERT [dbo].[Table_1] ([Id], [RelationId], [ParentId]) VALUES (1, N'0', 0)
INSERT [dbo].[Table_1] ([Id], [RelationId], [ParentId]) VALUES (2, N'1', 1)
INSERT [dbo].[Table_1] ([Id], [RelationId], [ParentId]) VALUES (3, N'1', 1)
INSERT [dbo].[Table_1] ([Id], [RelationId], [ParentId]) VALUES (4, N'1-3', 3)

View Code