complete newbe in PInvoke. I have a function in C with this signature: int addPos(int init_array_size, int *cnt, int *array_size, PosT ***posArray, PosT ***hPtr, char *id, char *record_id, int num, char *code, char *type, char *name, char *method, char *cont1, char *cont2, char *cont_type, char *date1, char *date_day, char *date2, char *dsp, char *curr, char *contra_acc, char *np, char *ten, char *dsp2, char *covered, char *cont_subtype, char *Xcode, double strike, int version, double t_price, double long, double short, double scale, double exrcised_price, char *infoMsg); and here is how PosT looks like: typedef union pu { struct dpos d; struct epo e; struct bpos b; struct spos c; } PosT ; my questions are: 1- do I need to define a class in CSharp representing PosT? 2- how do I pass PosT ***posArray parameter across frm CSharp to C? 3- How do I specify marshaling for it all? I Do appreciate your help