I'm writing my own serial number verification/protection for a software I wrote.
Assuming the serial number verifier is using pattern matching...once the serial number is verified, how can I change the program itself so that it doesn't ask the user for a serial number any longer?
I really don't want to have to create a separate license file. Is there a way to embed this within the program itself? Or is the registry the only other option (besides online verification, etc.)
You shouldn't really attempt to edit the program itself - it'll break signatures/strong-naming, the exe/dll file will almost certainly be locked, and even if you shadow-copy: many users won't have permission to edit it in program-files (or as click-once).
Something external such as a license file or registry setting seems appropriate (unless you want to build the app at your server per-client).