Hi I have 15 expertise in IT as a developer, designer and architect.
I don't have a degree in computer science but in mechanical engineering. What should be my Noc code. I found that this requires a degree in Computer science. http://noc.esdc.gc.ca/English/noc/Profile.aspx?val=2&val1=2173&ver=16
You don't need to prove you have that you have educational qualification for your job unless it's a regulated occupation like a pharmacist or doctor. IT occupations aren't regulated.
You can go ahead and select NOC 2173. In your Express Entry profile, you will be asked for "date applicant first became qualified to practice this occupation" you can enter the start date of your first 2173 job.