If you want that kind of power over a serial port try using interop with the kernel32 library. It will allow you to set everything you could possibly want to set. Problem is... interop, sort of defeats the purpose of C# but Ive found it very useful in my development with serial ports.
R.I.P. 3.5" Floppy Drives
"I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones." - Albert Einstein