在.NET中探測U盤的插入/拔出

有同學向我問這個問題，於是就Google了一下找到答案，不過是C下的，我將其改編成了C#的。

　　當設備被插入/拔出的時候，Windows會向每個窗體發送WM_DEVICECHANGE 消息，當消息的wParam 值等於 DBT_DEVICEARRIVAL 時，表示Media設備被插入並且已經可用；如果wParam值等於DBT_DEVICEREMOVECOMPLETE，表示Media設備已經被移出。

它們的lParam都指向一個 DEV_BROADCAST_HDR結構體，其原形如下：

1 typedef struct _DEV_BROADCAST_HDR
2 {
3     DWord dbch_size;
4     DWord dbch_devicetype;
5     DWord dbch_reserved;
6 } DEV_BROADCAST_HDR, *PDEV_BROADCAST_HDR;
這個結構體僅僅是一個“頭”（HDR），其後還有附加數據，dbch_size表示結構體實例的字節數，當其中的dbch_devicetype字段值等於DBT_DEVTYP_VOLUME時，表示當前設備是邏輯驅動器，且lParam實際上指向的應該是DEV_BROADCAST_VOLUME 結構體實例（真佩服這種邏輯），DEV_BROADCAST_VOLUME 結構體原形如下：


1 typedef struct _DEV_BROADCAST_VOLUME {
2     DWord dbcv_size;
3     DWord dbcv_devicetype;
4     DWord dbcv_reserved;
5     DWord dbcv_unitmask;
6     Word dbcv_flags;
7 } DEV_BROADCAST_VOLUME, *PDEV_BROADCAST_VOLUME;其中dbcv_unitmask 字段表示當前改變的驅動器掩碼，第一位表示驅動器號A，第二位表示驅動器號B，第三位表示驅動器號C，以此類推…… dbcv_flags 表示驅動器的類別，如果等於1，則是光盤驅動器；如果是2，則是網絡驅動器；如果是硬盤、U盤則都等於0

　　所以，我只需要在程序中捕捉WM_DEVICECHANGE 消息，然後根據具體情況去處理即可，下面是我的測試代碼：


using System;
using System.Runtime.InteropServices;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace UDiskDetect
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        [StructLayout(LayoutKind.Sequential)]
        struct DEV_BROADCAST_HDR
        {
            public UInt32 dbch_size;
            public UInt32 dbch_devicetype;
            public UInt32 dbch_reserved;
        }

        [StructLayout(LayoutKind.Sequential)]
        struct DEV_BROADCAST_VOLUME
        {
            public UInt32 dbcv_size;
            public UInt32 dbcv_devicetype;
            public UInt32 dbcv_reserved;
            public UInt32 dbcv_unitmask;
            public UInt16 dbcv_flags;
        }

        protected override void DefWndProc(ref Message m)
        {
            if (m.Msg == 0x0219)//WM_DEVICECHANGE
            {
                switch (m.WParam.ToInt32())
                {
                    case 0x8000://DBT_DEVICEARRIVAL
                        {
                            DEV_BROADCAST_HDR dbhdr = (DEV_BROADCAST_HDR)Marshal.PtrToStructure(m.LParam, typeof(DEV_BROADCAST_HDR));

                          if (dbhdr.dbch_devicetype == 0x00000002)//DBT_DEVTYP_VOLUME
                            {
                                DEV_BROADCAST_VOLUME dbv = (DEV_BROADCAST_VOLUME)Marshal.PtrToStructure(m.LParam, typeof(DEV_BROADCAST_VOLUME));
                                if (dbv.dbcv_flags == 0)
                                    AddVolumes(GetVolumes(dbv.dbcv_unitmask));
                            }
                            break;
                        }
                    case 0x8004://DBT_DEVICEREMOVECOMPLETE
                        {
                            DEV_BROADCAST_HDR dbhdr = (DEV_BROADCAST_HDR)Marshal.PtrToStructure(m.LParam, typeof(DEV_BROADCAST_HDR));

                            if (dbhdr.dbch_devicetype == 0x00000002)//DBT_DEVTYP_VOLUME
                         {
                                DEV_BROADCAST_VOLUME dbv = (DEV_BROADCAST_VOLUME)Marshal.PtrToStructure(m.LParam, typeof(DEV_BROADCAST_VOLUME));
                                if (dbv.dbcv_flags == 0)
                                    RemoveVolumes(GetVolumes(dbv.dbcv_unitmask));
                            }
                            break;
                        }
                }
            }
            base.DefWndProc(ref m);
        }

        /**//// <summary>
        /// 根據驅動器掩碼返回驅動器號數組
        /// </summary>
        /// <param name="Mask">掩碼</param>
        /// <returns>返回驅動器號數組</returns>
        public static char[] GetVolumes(UInt32 Mask)
        {
      List<char> Volumes = new List<char>();

            for (int i = 0; i < 32; i++)
            {
                uint p = (uint)Math.Pow(2, i);
                if ((p | Mask) == p)
                {
                    Volumes.Add((char)(''A'' + i));
                }
            }

            return Volumes.ToArray();
        }

        public void AddVolumes(char[] Volumes)
        {
            foreach (char volume in Volumes)
                listBox1.Items.Add(volume);
        }

 public void RemoveVolumes(char[] Volumes)
        {
            foreach (char volume in Volumes)
                listBox1.Items.Remove(volume);
        }

    }
}