C# and serial port

Dear all,
I don't find relevant anything about my question...is very simple.

I just try to create a very simple program in C# and Firmata library downloaded from the link founded into the doc section.
With this library I created an object of Arduino...ok...I pilot my digital pins...but how can read and write on the serial port? Is very simple as operation, but which is the command, the method...or is possible to read/write some strings?

Thanks very much in advace and forgive me for my bad english