I want to know how to get work visa for china.

Dear Sir,

I am in china on study visa now and I want to know how can I get work visa and do I need to come back to sri lanka or is it possible from here.And what are the all documents I need for that and and What documents I need from my work place and what type of support I need from them.And how much It will cost for me because I have to do everything by my self.So please send me all the information.

Thank you for your time and consideration,
Minidu Pasan