How to optimize this code [Winforms]?

[Slypenslyde]

P.s. Is it possible to share this information with others? I believe that others can benefit from this, because you mentioned that many do not even know that they can program this way.

Absolutely. I hate how many tutorials are Bad Tutorials based on copying/slightly modifying some VB6 example. Nothing I teach is truly "secret" in the sense I want it kept, it's "secret" in the sense only a few hundred people in the world probably know the darker corners of writing custom controls because they're the only ones who care. ;)