I believe it would be helpful if you told us which device you are using and what you are trying to accomplish, specifically. Maybe post a little code that you are having trouble with. Your description is quite vague.
While I have never tried interfacing with a serial port in C#, or Windows in general, I will try to help anyway. I worked on a project recently that involved interfacing with an Arduino board over its serial connection. For lack of further details on your part, I'm going to assume that your program will interface fairly similarly. I found this
blog post by John Ciacia that describes interacting with the Arduino in C# in great detail. In fact, the demonstration code in his post looks very similar to my own implementation (in C++ for Linux, however).
For the record, I had the same problem as you with the data received being somewhat slow. Essentially, you need to know exactly how many characters you need to read from the serial device before starting the read operation, and block until you receive that specific number of characters. In my case, I found it easiest to send and receive only one character at a time. That worked for me because I didn't have exceptionally complex instructions to carry out. Since your device's output sequence seems to be 3 integers followed by a space, that approach may work for you too (but waiting for four characters instead of just one before returning).
If you wish, I will post my class so you can look at how I solved the problem. Note, however, that it is in a different language for a different operating system, although the concepts should be fairly similar.
PS: Make sure you are initializing the connection with the correct baud rate. You will not be able to get anything done if the baud rate is wrong!