I have a question about user interface for Rhino Plugins. My question if I start creating a plugin with C# can I use C# standard UI “tools” that can appear in Rhino? Or what is the best way to create UI for a Rhino Plugin? I found this source so far: http://mkmra2.blogspot.kr/2012/12/creating-graphical-user-interfaces-with.html
The link you found is for python and is not what I would suggest for a C# developer.
If you are using C#, then I would suggest that you use either WPF or WinForms. Windows Forms is easier to learn, but WPF is more powerful and allows for better separation of interface and the logic behind the interface. We used to use WinForms a lot and are transitioning to all of our new C# user interface code being written with WPF.