If you have used the Visual Studio method of resource strings for i18n and you are moving to .NET I would strongly recommend you review how i18n resources work in .NET before you get into your project. The paradigm has changed, especially if you have multiple threads in a worker pool.
(Stop Reading because the Microsoft sales force has now taken over my brain...)
Resource Strings in .Net always have fallbacks. So in the above case the users thread would first ask for the Bokmal(nb-NO) version of the resource and if it wasn't there it would then fallback to the Norwegian (NO) version of the string and then fallback to my default resource file. (English en for me).
(more marketing BS...)
If this were my .Net app and I already had a Norwegian (NO) resource file (resmain.no.resx - a plain text XML file) I would copy the file to resmain.nb-NO.resx (Bokmal) and another copy as resmain.nn-NO.resx (Nynorsk). You can then pick and choose which resources you actually want to be different between them.
FYI:
no = Norwegian (x0014) (20)
nb-NO = Norwegian Bokmal (x0414) (1044)
nn-NO = Norwegian Nynorsk (x0814) (2068)