Recently i implement PAYONE payment using C# https://docs.payone.com/display/public/PLATFORM/PAYONE+Link+-+API I also work with other payment gateway like stripe. During develop this PAYONE solution for portal i realize myself this is no 1 according to their security. PAYONE is a very complex system but i like their sytem. PAYONE works like this steps: 1. Create link Request 2. Notify URL 3. Transaction status 4. Payment cancel request. soon i will try to share some code.
Work smarter, not harder.