Again, you can't send parameters to a running programm, that is simply not possible, and should not be! All you can do is send data to a specified address(in your case probably localhost/127.0.0.1) on a specified port. But the program must have a routine that recieves this data, and interprets it. To achieve this you have to use network functions. Exactly this is done in the patch, it adds support for telnet connections to the teeworlds server. If the server recieves data (via telnet with the port you specified and so on...) it processes it, meaning if it is a correct rcon command it executes this command, otherwise it will send you a message back, that you have entered an invalid command. So what you need to do is apply this patch to teeworlds and add some code to your program that lets it work as a telnet client(at least sort of).
So if you want your teeworlds server be controlled by another program, while allready running the only solution for you is to dig deeper into how network coding works, so you can let your program connect to the teeworlds server(protocol should be tcp/ip) and this way execute commands there. There is no other practicable way of doing this. I doubt the teeworlds community can help you much more with this issue, as we allready have told you about a (probably the best) solution. If you have further more questions about how to realize this whole networkthing i suggest you to read a tutorial on networkprogramming for your programming language(C#, if I understand your topic correctly), and for further questions ask in a forum that deals with this language, the'll probably be able to help you better, as those questions are probably not really tw specific.