Not that big deal....
RfcDestination dest = RfcDestinationManager.GetDestination("your_dest");
IRfcFunction rf = dest.Repository.CreateFunction("BAPI_CUSTOMER_GETDETAIL2");
rf.SetValue("CUSTOMERNO", "0000500002");
rf.Invoke(dest);
string n1 = rf.GetStructure("CUSTOMERADDRESS").GetString("NAME");