main.obj : error LNK2019: unresolved external symbol “__declspec(dllimport) public: __thiscall CNdisApi::CNdisApi(unsigned short const *)” (__imp_??0CNdisApi@@QAE@PBG@Z) referenced in function _main
The problem caused by -DUNICODE compiler switch. If you want your project to use UNICODE then you have to recompile ndisapi.dll as UNICODE either. For backward compatibility with earlier versions of Windows ndisapi.dll distributed within WinpkFilter package is built as multibyte.