I am looking for a snip of code in Blackberry 10 that my device is connected with n/w or not.
The official way is the Wi-Fi Service API, if you're familiar with C you should be good to go, look for any BPS tutorial/code online.
The unofficial and easier way is my class WifiWatcher from TheUnexposedAPIs, this project is a collection of easy-to-implement C++ classes that makes available all kind of internal objects from PPS (not to be confused with BPS).
You'll find an example of how to use it in QML in the project.