This program, which you showed was made in TMK (Trainer Maker Kit).
If you want make yur own tweak in C# you can use Process Memory Reader Lib (or discoveries own way to get into the process memory) and Cheat Engine (or other memory scanning tool) to find addresses.
It's sad that so many s2 users lately using hacks online.
I have a theory that if was released a new official patch not compatible with 0.6e, that could cause a momentary lack of such users online. Until someone would find it again:/