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If a detach a serial device which is still being used by windows, SerialPort.GetPortNames() will return that same detached device as actually still being attached. I also can't close the serial port without an unhandeled exception error stating that the port does not exist (which is true).

I can confirm that the device map for SERIALCOMM in the registry is not being updated either, which is where SerialPort.GetPortNames() gets the port names I presume. The hardware manager detects the right COMM ports.

Is there a way around this? Can I simply delete the SERIALCOMM registry entry? I looked at this potential workaround, but I think that will just let me catch the exception.

throwaway
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  • Possible duplicate: stackoverflow.com/questions/2754857/c-sharp-serialport-getportnames-behavior – tinman Nov 21 '11 at 20:42

1 Answers1

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I'm not an expert but my experience is that as long as you have any (SW-)object connected to the com-port it will be visible.

When I tested this some years ago I got the same result and not until I did lose my SerialPort object the port disappeared from the GetPortNames list (and presumable also the registry).

I think this is the way Windows handles this driver. If a serial port gets unplugged while in use in SW the system continues to have a place-holder for the serial port until it is released by SW.

In my SW I solved this by having a timeout for the function I needed (the other end could stop working as well) and before every new start of program-loop (normally once every 5min-1h) I just released the COM-port and reconnected to it, if reconnect failed the port was detected as lost...

Hope this helps you.

ATT
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