我正在写一个C#。NET应用程序，该应用程序访问公开串行端口接口的USB设备。我在用手电。NET SerialPort类，它工作得很好。
我的问题是，我需要捕获DBT_DEVICEQUERYREMOVE事件，但如果我使用DBT_DEVTYP_DEVICEINTERFACE注册，则无法获得该事件。我确实有DBT_DEVICEARRIVAL和DBT_DEVICEREMOVECOMPLETE，但没有DBT_DEVICEQUERYREMOVE。
从我的网络研究来看，我似乎需要使用DBT_DEVTYP_HANDLE注册，这需要一个句柄，比如CreateFile返回的句柄。由于SerialPort类没有公开这个句柄，我想知道是否有其他方法可以获取句柄（或者其他方法可以获得感兴趣的事件）。
我认为你可以使用一点反射来获得句柄，我不知道有什么更好的方法可以获得句柄。NET Framework当前正在使用。SerialPort使用一种称为SerialStream的内部类型。此Stream具有您想要的句柄。由于我没有可以测试的串行端口，所以这段代码有点像猜测：
var serialPort = new SerialPort();
object stream = typeof(SerialPort).GetField("internalSerialStream", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(serialPort);
var handle = (SafeFileHandle)stream.GetType().GetField("_handle", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(stream);
这将为您提供一个SafeFileHandle，它是句柄的包装器。您可以调用DangerousGetHandle来获得实际的IntPtr。
此句柄只有在SerialPort上调用Open之后才具有有效值，并且在释放时变为无效。在使用DangerousGetHandle之前，应该先检查句柄的IsInvalid和IsClosed值。
还有一个解决方案是获取的Serialport实现。Net并根据您的喜好进行更改。
这是我为一个需要访问句柄的项目所做的，因为我在SerialPort中遇到了定时/异步问题。所以我把它归结为熊的必需品。
public class SimpleSerialPort : IDisposable
{
private const uint GenericRead = 0x80000000;
private const uint GenericWrite = 0x40000000;
private const int OpenExisting = 3;
private const uint Setdtr = 5; // Set DTR high
private FileStream _fileStream;
public void Close()
{
Dispose();
}
public int WriteTimeout { get; set; }
public SafeFileHandle Handle { get; private set; }
public void Open(string portName, uint baudrate)
{
// Check if port can be found
bool isValid =
SerialPort.GetPortNames()
.Any(x => String.Compare(x, portName, StringComparison.OrdinalIgnoreCase) == 0);
if (!isValid)
{
throw new IOException(string.Format("{0} port was not found", portName));
}
string port = @"\." + portName;
Handle = CreateFile(port, GenericRead | GenericWrite, 0, IntPtr.Zero, OpenExisting, 0, IntPtr.Zero);
if (Handle.IsInvalid)
{
throw new IOException(string.Format("{0} port is already open", portName));
}
var dcb = new Dcb();
// first get the current dcb structure setup
if (GetCommState(Handle, ref dcb) == false)
{
throw new IOException(string.Format("GetCommState error {0}", portName));
}
dcb.BaudRate = baudrate;
dcb.ByteSize = 8;
dcb.Flags = 129;
dcb.XoffChar = 0;
dcb.XonChar = 0;
/* Apply the settings */
if (SetCommState(Handle, ref dcb) == false)
{
throw new IOException(string.Format("SetCommState error {0}", portName));
}
/* Set DTR, some boards needs a DTR = 1 level */
if (EscapeCommFunction(Handle, Setdtr) == false)
{
throw new IOException(string.Format("EscapeCommFunction error {0}", portName));
}
// Write default timeouts
var cto = new Commtimeouts
{
ReadTotalTimeoutConstant = 500,
ReadTotalTimeoutMultiplier = 0,
ReadIntervalTimeout = 10,
WriteTotalTimeoutConstant = WriteTimeout,
WriteTotalTimeoutMultiplier = 0
};
if (SetCommTimeouts(Handle, ref cto) == false)
{
throw new IOException(string.Format("SetCommTimeouts error {0}", portName));
}
// Create filestream
_fileStream = new FileStream(Handle, FileAccess.ReadWrite, 32, false);
}
public void Write(byte[] bytes)
{
_fileStream.Write(bytes, 0, bytes.Length);
}
public void Read(byte[] readArray)
{
for (int read = 0; read < readArray.Length;)
{
read += _fileStream.Read(readArray, read, readArray.Length - read);
}
}
public byte ReadByte()
{
byte[] readsBytes = new byte[1];
Read(readsBytes);
return readsBytes[0];
}
public void Dispose()
{
if (Handle != null)
{
Handle.Dispose();
}
if (_fileStream != null)
{
_fileStream.Dispose();
}
_fileStream = null;
Handle = null;
}
[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern SafeFileHandle CreateFile(string lpFileName, uint dwDesiredAccess, int dwShareMode,
IntPtr securityAttrs, int dwCreationDisposition, int dwFlagsAndAttributes, IntPtr hTemplateFile);
[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
private static extern bool GetCommState(
SafeFileHandle hFile, // handle to communications device
ref Dcb lpDcb // device-control block
);
[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern bool SetCommState(
SafeFileHandle hFile, // handle to communications device
ref Dcb lpDcb // device-control block
);
[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern bool EscapeCommFunction(
SafeFileHandle hFile, // handle to communications device
uint dwFunc
);
[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
private static extern bool SetCommTimeouts(
SafeFileHandle hFile, // handle to comm device
ref Commtimeouts lpCommTimeouts // time-out values
);
[StructLayout(LayoutKind.Sequential)]
private struct Commtimeouts
{
public int ReadIntervalTimeout;
public int ReadTotalTimeoutMultiplier;
public int ReadTotalTimeoutConstant;
public int WriteTotalTimeoutMultiplier;
public int WriteTotalTimeoutConstant;
}
[StructLayout(LayoutKind.Sequential)]
private struct Dcb
{
private readonly uint DCBlength;
public uint BaudRate;
public uint Flags;
private readonly ushort WReserved;
private readonly ushort XonLim;
private readonly ushort XoffLim;
public byte ByteSize;
private readonly byte Parity;
private readonly byte StopBits;
public byte XonChar;
public byte XoffChar;
private readonly byte ErrorChar;
private readonly byte EofChar;
private readonly byte EvtChar;
private readonly ushort WReserved1;
}
}