可以看到，项的前面都显示了加号(+),而且读取了磁盘的文件。代码如下

主程序代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
namespace FileManager
{
    public partial class Main : Form
    {
        public Main()
        {
            InitializeComponent();
        }
        /// <summary>
        /// 加载逻辑磁盘文件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void Main_Load(object sender, EventArgs e)
        {
            DriveInfo[] myDrivers = DriveInfo.GetDrives();
            foreach (DriveInfo di in myDrivers)
            {
                if (di.IsReady)
                {
                    TreeNode tNode = new TreeNode(di.Name.Split(':')[0]);
                    tNode.Name = di.Name;
                    tNode.Tag = tNode.Name;
                    tNode.Nodes.Add("DUMMY");
                    tvRoot.Nodes.Add(tNode);
                }
            }
            //添加鼠标右键的事件
            this.tvRoot.ContextMenuStrip = new TreeViewContextMenu().Load();
        }

        /// <summary>
        /// TreeView必须处理的两个事件之一
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void tvRoot_AfterSelect(object sender, TreeViewEventArgs e)
        {
            e.Node.Expand();
        }

        /// <summary>
        /// TreeView必须处理的两个事件之一
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void tvRoot_BeforeExpand(object sender, TreeViewCancelEventArgs e)
        {
            TreeViewItems.Add(sender, e);
        }
    }
}

为TreeView添加TreeNode的代码：

public static  class TreeViewItems
    {
       public static void Add(object sender, TreeViewCancelEventArgs e)
       {
           e.Node.Nodes.Clear();
           TreeNode tNode = e.Node;
           //MessageBox.Show(tNode.Name);
           string path = tNode.Name;
           string[] dics = Directory.GetDirectories(path);
           foreach (string dic in dics)
           {
               TreeNode subNode = new TreeNode(new DirectoryInfo(dic).Name);
               subNode.Name = new DirectoryInfo(dic).FullName;
               subNode.Tag = subNode.Name;
               subNode.Nodes.Add("");
               tNode.Nodes.Add(subNode);

           }
           string[] files = Directory.GetFiles(path);
           foreach (string aFile in files)
           {
               TreeNode subNode = new TreeNode(new FileInfo(aFile).Name);
               subNode.Tag = aFile;
               subNode.Name = subNode.Text;
               tNode.Nodes.Add(subNode);
           }
       }
    }

这里注意e.Node.Nodes.Clear();还有给节点的下面添加一个空的节点：如

tNode.Nodes.Add