Thanks for using MonoBrick firmware!
I am not sure if I understand your problem correctly. But in order to create your own project you need to add a reference to the firmware dll. Then you need to make sure that the dll is copied to the output folder. When you “transfer/copy” the program to the brick – you need to make sure that the dll is also copied. Otherwise there will be a mismatch between the dll that was used for compiling the program and the dll that is used at runtime…