Cannot get "OpenDoc6" to work in C#, am I doing something wrong?

Just cannot make the following to work, it returns a few error:

long errors, warnings;

swModel = swApp.OpenDoc6(fileName, SwConst.swDocumentTypes_e.swDocASSEMBLY, SwConst.swOpenDocOptions_e.swOpenDocOptions_Silent, "", errors, warnings);

Can someone please help thanks!!!

SolidworksApi macros