One way to make variable values persist in WinForms is to use Application.Settings: [
^].
There's a good tutorial here on CodeProject on how to use Application.Settings: [
^].
However, I suggest you only use Application.Settings for exactly what that name implies: global settings for your Applcation: things like default BackGroundColor, Font, Window Sizes, etc.
If you have a lot of variables whose value you wish to store across sessions, then I think you should create a Class to hold those variables and their values and serialize the Class to a file, and then de-serialize it when your Application starts.
There are many good examples that show/teach you how to serialize and de-serialize a Class on CodeProject.