问题描述
我正在使用 .NET 4 SerialPort 对象与连接到 COM1 的设备通信.
I am using a .NET 4 SerialPort object to talk to a device attached to COM1.
设备完成后，我在 SerialPort 上调用 Close.我不叫 Dispose，但我相信 Close 和 Dispose 在这里是同义词.
When I am done with the device, I call Close on the SerialPort. I do not call Dispose, but I believe that Close and Dispose are synonymous here.
通常这很好用.
然而，有时我会在一段时间后收到以下异常(我看到的时间范围从 5 毫秒到 175 毫秒):
Sometimes, however, I get the following exception some time later (The times I've seen range from 5 ms to 175 ms):
System.ObjectDisposedException: Safe handle has been closed
at System.Runtime.InteropServices.SafeHandle.DangerousAddRef(Boolean& success)
at System.StubHelpers.StubHelpers.SafeHandleAddRef(SafeHandle pHandle, Boolean& success)
at Microsoft.Win32.UnsafeNativeMethods.GetOverlappedResult(SafeFileHandle hFile, NativeOverlapped* lpOverlapped, Int32& lpNumberOfBytesTransferred, Boolean bWait)
at System.IO.Ports.SerialStream.EventLoopRunner.WaitForCommEvent()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()我的代码都不在这个堆栈上.
None of my code is on this stack.
我发现 http://blog.zachsaw.com/2010/07/serialport-ioexception-workaround-in-c.html，但那里的解决方案不起作用.进一步检查，问题是 IOException，而不是 ObjectDisposedException.
I found http://blog.zachsaw.com/2010/07/serialport-ioexception-workaround-in-c.html, but the solution there did not work. On further inspection, the issue there is an IOException, not an ObjectDisposedException.
关于当 USB 转串口设备被拔出但 COM1 是板载的，所以它不会意外消失时观察到的问题的帖子太多了.
There are a plethora of posts concerning issues observed when a USB-to-serial device is unplugged, but COM1 is onboard, so it isn't vanishing unexpectedly.
这里的问题也不是我的问题;SerialPort 在其使用期间保持活动状态，并且仅在我与设备通话完毕时才关闭.(完成后，设备处于不会传输任何进一步数据的状态.)
The problem here is also not my issue; the SerialPort is kept alive for the duration of its use, and is closed only when I am done talking to the device. (Once I am done, the device is in a state where it will not transmit any further data.)
SLaks建议在SerialPort.Close 的一次调用会调用三次，其余大约一半在 GC 线程中.其余部分似乎与 WPF UI 元素有关.
SLaks suggests setting a breakpoint on the entrance to SafeHandle.Dispose, to determine when I'm disposing something I shouldn't be, but I strike that breakpoint dozens of times. Three times are called by my single call to SerialPort.Close, when I am done using the serial device, and about half the rest are in the GC thread. The remainder seem to be related to WPF UI elements.
我现在不知所措.我从这里去哪里?
I am now at a loss. Where do I go from here?
有没有办法确定哪个 SafeHandle 属于哪个对象，这样我就可以确定我不会意外处置它?
除了关闭之外，还有什么咒语需要正确关闭 SerialPort 吗?
Is there a way to determine which SafeHandle belongs to which object, so I can be certain I'm not disposing it unexpectedly?
Is there some incantation other than Close I need to properly shut down a SerialPort?
推荐答案
我也遇到过这个问题，自从我开始使用以下两个规则后就再也没有遇到过.
I've had this issue too, and since I started using the following two rules I've never seen it again.
- 始终调用 Close()，然后调用 Dispose().
- 永远不要重复使用 SerialPort 对象，当需要重新打开端口时始终创建一个新对象.
我知道，它们不是什么新闻，但它一直在为我工作.
I know, they aren't much news, but its been working for me.
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