Serial Port Cable Unplugged
.net, serial-port
Solution
Unlike USB, the serial port does not have any built-in way to detect a physical change in link status. A limited form of "device ready/not ready" signalling can be done using some of the pins (namely DTR, DSR, and sometimes DCD), but this doesn't seem like exactly what you're looking for (it's not built in to RS232 -- the device must support it, you mainly use it to talk to modems.)
So, in short: no, in the general case. If you know/can program the device you're trying to communicate with, and you know that it will hold a certain line high (for example), you could poll it looking for that line to go high. But if you plug in a device which isn't programmed to do something predictable like that, then there's really no way to tell. (Some devices may hold DSR high by default but it's in no way a sure bet.)
Problem
In .Net's SerialPort object, is there a way to determine if a serial port gets unplugged or plugged in.