So what do you want to save for the value? A bit field (good idea), the words "True" or False, "Yes" or "No" (bad ideas)
The code you posted is not doing a great deal of good, you are clearly heading down the road to SQL Injection land - SQL Injection - OWASP
]. Use the correct techniques - Injection Prevention Cheat Sheet - OWASP
]. Use parameterised queries!
You are also building up a comma-separated list of the checkbox text not the values. Even if you were using the right property storing anything as a comma-separated list in a database is a Bad Idea. Give each text box it's own column.. it is much, much easier to get information in and out of the database that way.
In the bottom right corner of this page is a list of "Related Questions" - try the solutions there first (that is partly what we mean by "do some research"), write some proper code and try it out. If you are still having problems after that come back (with your code) and we will try to help you further.
When you do come back avoid using terms like "plzz hlp me". The words are "please" and "help" - not everyone has English as their first language and using text-speak just makes it harder for them to understand your question - and that means they won't be able to (or inclined to) help you