I once wrote an C# application that read bytes from the serial port and sent them out as midi.
What I used was the FullDuplexSerial object and the serial library available in .NET. You will have to define what you're sending so the other side can correctly parse it.
Parallax created an app note with examples. You can find the app notes on the QuickStart page in the downloads section. http://www.parallax.com/product/40000
Jan Axelson has some simple VB programs on her web site (http://janaxelson.com). She was targeting the PIC in her example from a magazine article, but it's very easy to adapt the microcontroller end to the Propeller.
Comments
What I used was the FullDuplexSerial object and the serial library available in .NET. You will have to define what you're sending so the other side can correctly parse it.
http://www.parallax.com/product/40000
A direct link to the app Note
http://www.parallax.com/downloads/an018-communication-pc-application