hide code in plugin(4.17)

How can i hide code in my plugin?
i delete the source and intermediate file in my plugin and it works fine.But when i packaged the project,something went wrong.
It said:UATHelper: Packaging (Windows (64-bit)): UnrealBuildTool: ERROR: Couldn’t find module rules file for module ‘myplugin’.I am using 4.17

IIrc, you should keep your .Build.cs file

Compile the code into library (static or dynamic) and have them included in the build

Keep the Build.cs files, can’t delete them.
Btw, people most likely won’t buy your plugin without source included.

Where shoud i put the .build.cs file?
i keep the source file and put the .build.cs in it,but this did not work.