COMPORT now I use serial port controls, I want to ask is, turn the USB serial port, if there are any in use has been pulled out, is that COM is invalid, want how to deal with, such events, now the software before closing, the customer first unplug the USB, resulting in abnormal WINDOWS popup dialog box,

Note, I use other's software, intentionally this class, its reaction is very friendly, just prompt the serial port is invalid, no strong play, an error dialog,