我需要在USB驱动器上创建一个记录文件活动。
到目前为止我能做些什么：
使用ManagementEventWatcher检测USB存储器的插入和提取（检测到内存被移除后的提取）：
using System.Management;
var insertQuery = new WqlEventQuery("SELECT * FROM Win32_VolumeChangeEvent WHERE EventType = 2");
var insertWatcher = new ManagementEventWatcher(insertQuery);
insertWatcher.EventArrived += DeviceInsertedEvent;
insertWatcher.Start();
使用FileSystemWatcher我可以录制所有动作，例如。创建，修改，删除和重命名的文件：
FileSystemWatcher m_Watcher = new FileSystemWatcher();
m_Watcher.Path = e.PathDevice + "\\";
string strFilter = "*.*";
m_Watcher.Filter = strFilter;
m_Watcher.NotifyFilter =
NotifyFilters.Attributes |
NotifyFilters.FileName;
m_Watcher.IncludeSubdirectories = true;
m_Watcher.Created += new FileSystemEventHandler(OnCreated);
m_Watcher.EnableRaisingEvents = true;
问题：
当FileSystemWatcher正在查看该单元时，如果我尝试安全地弹出该单元，它会告诉我我不能，因为我的应用程序正在使用它。设置为true EnableRaisingEvents = true;时，此变量使事件能够侦听内存中的更改，并且不允许我安全地删除内存，我进行了测试并启动应用程序并将其设置为false EnableRaisingEvents = false;我可以安全地删除内存。
可能的解决方案：
如何在操作系统删除设备之前检测设备的删除？这样我就可以停止在设备上使用FileSystemWatcher并安全地移除USB设备。
答案 0 :(得分：1)
经过几天寻找种植问题的答案我找到了解决方案。
This article对解决问题非常有帮助and this。
如果我们使用服务或windows form application，解决方案会发生变化。 我的回答基于服务 。
服务有一个控制处理程序，它接收来自Windows的所有消息。这些可能包括停止或暂停服务的代码，或者在我们的例子中，包括设备事件。我们需要注册我们自己的服务处理程序，因此我们可以捕获设备事件。除了OnStart之外，这将禁用所有回调，例如OnStop，在我们告诉Windows使用我们的处理程序之前调用它。
Windows API函数是RegisterServiceCtrlHandlerEx，它接受服务名称和回调函数，以便在收到消息时调用。我们将在我们服务的OnStart函数中调用它。
服务控制处理程序的签名如下：
public delegate int ServiceControlHandlerEx（int control，int eventType， IntPtr eventData，IntPtr context）;
public partial class Service1 : ServiceBase{
private FileSystemWatcher fileSystemWatcher;
private IntPtr deviceNotifyHandle;
private IntPtr deviceEventHandle;
private IntPtr directoryHandle;
private Win32.ServiceControlHandlerEx myCallback;
public Service1()
{
InitializeComponent();
}
protected override void OnStart(string[] args)
{
base.OnStart(args);
//
RegisterDeviceNotification();
fileSystemWatcher = new FileSystemWatcher();
fileSystemWatcher.Created += new System.IO.FileSystemEventHandler(fileSystemWatcher_Created);
fileSystemWatcher.Deleted += new System.IO.FileSystemEventHandler(fileSystemWatcher_Deleted);
fileSystemWatcher.Changed += new System.IO.FileSystemEventHandler(fileSystemWatcher_Changed);
fileSystemWatcher.Renamed += new System.IO.RenamedEventHandler(fileSystemWatcher_Renamed);
}
}
注册设备通知
在OnStart方法中，除了注册控制处理程序外，我们还会使用Win32 API函数RegisterDeviceNotification注册设备通知。我们给它提供服务的句柄，一个指向DEV_BROADCAST_DEVICEINTERFACE结构的指针（告诉函数注册一类设备），以及一些标志，其中包括DEVICE_NOTIFY_SERVICE_HANDLE，它指定调用者是例如，服务而不是窗口。它返回一个句柄，我们必须保留这个句柄，以便在我们不再需要设备消息时取消注册（例如，我们可以在SERVICE_CONTROL_STOP事件中执行此操作。）
使用此功能可以捕获DBT_DEVICEARRIVAL和DBT_DEVICEREMOVECOMPLETE事件类型。我们通过服务控制处理程序的eventType参数获取它们。在那里，我们可以处理SERVICE_CONTROL_DEVICEEVENT并做任何我们喜欢的事情。
public void RegisterDeviceNotification()
{
InitArrayDevNotifyHandle();
myCallback = new Win32.ServiceControlHandlerEx(ControlHandler);
Win32.RegisterServiceCtrlHandlerEx(service.ServiceName, myCallback, IntPtr.Zero);
if (service.GetServiceHandle() == IntPtr.Zero)
{
// TODO handle error
}
Win32.DEV_BROADCAST_DEVICEINTERFACE deviceInterface = new Win32.DEV_BROADCAST_DEVICEINTERFACE();
int size = Marshal.SizeOf(deviceInterface);
deviceInterface.dbcc_size = size;
deviceInterface.dbcc_devicetype = Win32.DBT_DEVTYP_DEVICEINTERFACE;
IntPtr buffer = default(IntPtr);
buffer = Marshal.AllocHGlobal(size);
Marshal.StructureToPtr(deviceInterface, buffer, true);
deviceEventHandle = Win32.RegisterDeviceNotification(service.GetServiceHandle(), buffer, Win32.DEVICE_NOTIFY_SERVICE_HANDLE | Win32.DEVICE_NOTIFY_ALL_INTERFACE_CLASSES);
if (deviceEventHandle == IntPtr.Zero)
{
// TODO handle error
}
}
DBT_DEVICEQUERYREMOVE - 解决方案
这是回答这个问题的主要内容
我需要通知应用对设备硬件配置的更改。特别是在SO之前更换USB存储器将删除内存。感谢@ZdeněkJelínek，我能够找到要求许可删除设备或介质的事件DBT_DEVICEQUERYREMOVE。此事件即将在设备即将被移除之前举行。
解决方案是创建设备本身的句柄，在DEV_BROADCAST_HANDLE结构中使用它，并将其注册到我们的服务控制处理程序。为了实现这一切，需要做几件事：
查找设备的驱动器号。我能够使用ManagementEventWatcher类，它允许我订阅设备插入事件，它为我提供了有关插入设备的信息。
所有这些都是通过使用CreateFileHandle函数获取设备句柄来完成的。只有在此之后我们才能获得DBT_DEVICEQUERYREMOVE事件，禁用FileSystemWatcher，并允许自由删除USB。
private int ControlHandler(int control, int eventType, IntPtr eventData, IntPtr context)
{
if (control == Win32.SERVICE_CONTROL_STOP || control == Win32.SERVICE_CONTROL_SHUTDOWN)
{
UnregisterHandles();
Win32.UnregisterDeviceNotification(deviceEventHandle);
base.Stop();
}
else if (control == Win32.SERVICE_CONTROL_DEVICEEVENT)
{
string c;
switch (eventType)
{
case Win32.DBT_DEVICEARRIVAL:
//This is an example ... I do not use the DBT_DEVICEARRIVAL event, but it can be used. Instead use the ManagementEventWatcher class to detect when a device arrives and driveLetter.
RegisterForHandle(driveLetter);
fileSystemWatcher.Path = driveLetter + ":\\";
fileSystemWatcher.EnableRaisingEvents = true;
break;
case Win32.DBT_DEVICEQUERYREMOVE:
Win32.DEV_BROADCAST_HDR hdrR;
Win32.DEV_BROADCAST_HANDLE dbhdl;
hdrR = (Win32.DEV_BROADCAST_HDR)
Marshal.PtrToStructure(eventData, typeof(Win32.DEV_BROADCAST_HDR));
if (hdrR.dbcc_devicetype == Win32.DBT_DEVTYP_HANDLE)
{
dbhdl = (Win32.DEV_BROADCAST_HANDLE)
Marshal.PtrToStructure(eventData, typeof(Win32.DEV_BROADCAST_HANDLE));
UnregisterHandles();
fileSystemWatcher.EnableRaisingEvents = false;
fileSystemWatcher = null;
}
break;
}
}
return 0;
}
private void UnregisterHandles()
{
if (directoryHandle != IntPtr.Zero)
{
Win32.CloseHandle(directoryHandle);
directoryHandle = IntPtr.Zero;
}
if (deviceNotifyHandle != IntPtr.Zero)
{
Win32.UnregisterDeviceNotification(deviceNotifyHandle);
deviceNotifyHandle = IntPtr.Zero;
}
}
private void RegisterForHandle(char c)
{
Win32.DEV_BROADCAST_HANDLE deviceHandle = new Win32.DEV_BROADCAST_HANDLE();
int size = Marshal.SizeOf(deviceHandle);
deviceHandle.dbch_size = size;
deviceHandle.dbch_devicetype = Win32.DBT_DEVTYP_HANDLE;
directoryHandle = CreateFileHandle(c + ":\\");
deviceHandle.dbch_handle = directoryHandle;
IntPtr buffer = Marshal.AllocHGlobal(size);
Marshal.StructureToPtr(deviceHandle, buffer, true);
deviceNotifyHandle = Win32.RegisterDeviceNotification(this.ServiceHandle, buffer, Win32.DEVICE_NOTIFY_SERVICE_HANDLE);
if (deviceNotifyHandle == IntPtr.Zero)
{
// TODO handle error
}
}
public static IntPtr CreateFileHandle(string driveLetter)
{
// open the existing file for reading
IntPtr handle = Win32.CreateFile(
driveLetter,
Win32.GENERIC_READ,
Win32.FILE_SHARE_READ | Win32.FILE_SHARE_WRITE,
0,
Win32.OPEN_EXISTING,
Win32.FILE_FLAG_BACKUP_SEMANTICS | Win32.FILE_ATTRIBUTE_NORMAL,
0);
if (handle == Win32.INVALID_HANDLE_VALUE)
{
return IntPtr.Zero;
}
else
{
return handle;
}
}
public class Win32
{
public const int DEVICE_NOTIFY_SERVICE_HANDLE = 1;
public const int DEVICE_NOTIFY_ALL_INTERFACE_CLASSES = 4;
public const int SERVICE_CONTROL_STOP = 1;
public const int SERVICE_CONTROL_DEVICEEVENT = 11;
public const int SERVICE_CONTROL_SHUTDOWN = 5;
public const uint GENERIC_READ = 0x80000000;
public const uint OPEN_EXISTING = 3;
public const uint FILE_SHARE_READ = 1;
public const uint FILE_SHARE_WRITE = 2;
public const uint FILE_SHARE_DELETE = 4;
public const uint FILE_ATTRIBUTE_NORMAL = 128;
public const uint FILE_FLAG_BACKUP_SEMANTICS = 0x02000000;
public static readonly IntPtr INVALID_HANDLE_VALUE = new IntPtr(-1);
public const int DBT_DEVTYP_DEVICEINTERFACE = 5;
public const int DBT_DEVTYP_HANDLE = 6;
public const int DBT_DEVICEARRIVAL = 0x8000;
public const int DBT_DEVICEQUERYREMOVE = 0x8001;
public const int DBT_DEVICEREMOVECOMPLETE = 0x8004;
public const int WM_DEVICECHANGE = 0x219;
public delegate int ServiceControlHandlerEx(int control, int eventType, IntPtr eventData, IntPtr context);
[DllImport("advapi32.dll", SetLastError = true)]
public static extern IntPtr RegisterServiceCtrlHandlerEx(string lpServiceName, ServiceControlHandlerEx cbex, IntPtr context);
[DllImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool GetVolumePathNamesForVolumeNameW(
[MarshalAs(UnmanagedType.LPWStr)]
string lpszVolumeName,
[MarshalAs(UnmanagedType.LPWStr)]
string lpszVolumePathNames,
uint cchBuferLength,
ref UInt32 lpcchReturnLength);
[DllImport("kernel32.dll")]
public static extern bool GetVolumeNameForVolumeMountPoint(string
lpszVolumeMountPoint, [Out] StringBuilder lpszVolumeName,
uint cchBufferLength);
[DllImport("user32.dll", SetLastError = true)]
public static extern IntPtr RegisterDeviceNotification(IntPtr IntPtr, IntPtr NotificationFilter, Int32 Flags);
[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern uint UnregisterDeviceNotification(IntPtr hHandle);
[DllImport("kernel32.dll", SetLastError = true)]
public static extern IntPtr CreateFile(
string FileName, // file name
uint DesiredAccess, // access mode
uint ShareMode, // share mode
uint SecurityAttributes, // Security Attributes
uint CreationDisposition, // how to create
uint FlagsAndAttributes, // file attributes
int hTemplateFile // handle to template file
);
[DllImport("kernel32.dll", SetLastError = true)]
public static extern bool CloseHandle(IntPtr hObject);
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct DEV_BROADCAST_DEVICEINTERFACE
{
public int dbcc_size;
public int dbcc_devicetype;
public int dbcc_reserved;
[MarshalAs(UnmanagedType.ByValArray, ArraySubType = UnmanagedType.U1, SizeConst = 16)]
public byte[] dbcc_classguid;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 128)]
public char[] dbcc_name;
}
[StructLayout(LayoutKind.Sequential)]
public struct DEV_BROADCAST_HDR
{
public int dbcc_size;
public int dbcc_devicetype;
public int dbcc_reserved;
}
[StructLayout(LayoutKind.Sequential)]
public struct DEV_BROADCAST_HANDLE
{
public int dbch_size;
public int dbch_devicetype;
public int dbch_reserved;
public IntPtr dbch_handle;
public IntPtr dbch_hdevnotify;
public Guid dbch_eventguid;
public long dbch_nameoffset;
public byte dbch_data;
public byte dbch_data1;
}
}