1、代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace TestApp
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }

        private void BtnConfig_Click(object sender, EventArgs e)
        {
            treeView1.Nodes.Clear();
            string root = TbRoot.Text;
            if(Directory.Exists(root) )
            {
                TreeNode treeNode = new TreeNode(root);
                treeView1.Nodes.Add(treeNode);
                FindDirectory(root, treeNode);
            }
            else
            {
                MessageBox.Show("输入目录不存在！");
                TbRoot.Clear();
                treeView1.Nodes.Clear();
            }
        }

        private void FindDirectory(string root, TreeNode parentNode)
        {
            try
            {
                string[] arr = Directory.GetDirectories(root);
                if (arr.Length > 0)
                {
                    foreach (string item in arr)
                    {
                        string str = Path.GetFileNameWithoutExtension(item);
                        TreeNode node = new TreeNode(str);
                        parentNode.Nodes.Add(node);
                        FindDirectory(item, node);
                    }
                }
            }catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

        TreeNode currentNode = null;
        private void treeView2_AfterSelect(object sender, TreeViewEventArgs e)
        {
            currentNode = e.Node;
        }

        int i = 0;
        private void BtnAddNode_Click(object sender, EventArgs e)
        {
            if (treeView2.Nodes.Count > 0)
            {
                TreeNode node = new TreeNode($"节点{i++}");
                currentNode.Parent.Nodes.Add(node);
            }
            else
            {
                TreeNode node = new TreeNode("首节点");
                treeView2.Nodes.Add(node);
            }
        }

        private void BtnAddSonNode_Click(object sender, EventArgs e)
        {
            if (treeView2.Nodes.Count > 0)
            {
                TreeNode node = new TreeNode($"节点{i++}");
                currentNode.Nodes.Add(node);
            }
        }

        private void BtnDeleteNode_Click(object sender, EventArgs e)
        {
            treeView2.Nodes.Remove(currentNode);
        }
    }
}

2、运行结果