How is it possible to declare a path to a source within the app folder?

For example if a add a assembly that is somewhere in the project dir, though that the path declared is the full path, if I move the dir to another location the path changes with it.

I now want to add a path to a local db file that exists in the project dir that I will deliver(execs&assemblies only).
The Environment.CurrentFolder returns the path to the bin dir.
The folder that contains the file is a level above