How does C open and read the file directory of usb

Below I through a small example and combined with a fragment of code to show you under the need of friends can learn from it.

Drag 1 button and treeview on the interface, insert USB flash drive directly when running, and the directory file will appear on the stand-alone button. However, information can only be received when u disk is inserted and U disk is unplugged.
1. [C #] Code

using System;
using System.Collections;
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;
using System.Threading.Tasks;
using System.Windows.Forms;
 namespace usbText
{
 public partial class Form1 : Form
 {
 DriveInfo Tdriver = null;
 public Form1()
 {
 InitializeComponent();
 }
 protected override void WndProc(ref Message m)
 {
 if (m.Msg == 0x0219)//WM_DEVICECHANGE
 {
 switch (m.WParam.ToInt32())
 {
  case 0x8000://DBT_DEVICEARRIVAL
  {
  MessageBox.Show(" Device insertion ");
  string[] dirs = Environment.GetLogicalDrives(); // Get all the drive letters  
  foreach (string dir in dirs)
  {
   Tdriver = new DriveInfo(dir);
   if (Tdriver.DriveType == DriveType.Removable)
   {
   {
   while (Tdriver.IsReady == false)
   {
   Thread.Sleep(500);
   }
   try
   {
   string PSTR = "";
   PSTR += " Disk name: " + Tdriver.Name + "\r\n";
   PSTR += " Disk Volume Label: " + Tdriver.VolumeLabel + "\r\n";
   PSTR += " File system: " + Tdriver.DriveFormat + "\r\n";
   PSTR += " Remaining size: " + Tdriver.AvailableFreeSpace.ToString() + "\r\n";
   PSTR += " Total capacity: " + Tdriver.TotalSize.ToString() + "\r\n";
   PSTR += " Total capacity: " + Tdriver.RootDirectory.ToString() + "\r\n";
   MessageBox.Show(PSTR);
   }
   catch
   {
   MessageBox.Show("error");
   }
   }
   }
  } 
  break;
  }
  case 0x8004://DBT_DEVICEREMOVECOMPLETE
  {
  MessageBox.Show(" Equipment pull-out ");
  break;
  }
 }
 }
 base.WndProc(ref m);
 }
 private void AddToTreeView(TreeNode node)
 {
 treeView1.Nodes.Add(node);
 treeView1.Refresh();
 }
 internal void LoadFolderFileList(string path, TreeNode nodes)
 {
 string[] dirs = Directory.GetDirectories(path);
 string[] files = Directory.GetFiles(path);
 for (int i = 0; i < dirs.Length; i++)
 {
 string[] info = new string[4];
 DirectoryInfo di = new DirectoryInfo(dirs[i]);
 TreeNode node = new TreeNode(di.Name);
 node.Tag = di.FullName;
 try
 {
  if (di.GetDirectories().Length > 0 || di.GetFiles().Length > 0)
  {
  LoadFolderFileList(di.FullName, node);
  }
  else
  {
  continue;
  }
 }
 catch
 {
  continue;
 }
 nodes.Nodes.Add(node);
 }
 for (int i = 0; i < files.Length; i++)
 {
 FileInfo fi = new FileInfo(files[i]);
 TreeNode node = new TreeNode(fi.Name);
 node.Tag = fi.FullName;
 nodes.Nodes.Add(node);
 }
 }
 private void button1_Click(object sender, EventArgs e)
 {
 if (Tdriver != null)
 {
 TreeNode node = new TreeNode();
 LoadFolderFileList(Tdriver.RootDirectory.ToString(), node);
 treeView1.Nodes.Add(node);
 }
 }
 }
}

Through the above code can be opened and read usb file directory, I hope you can like it.