Use VI already running using ActiveX

Question

  Is there a way to make it fail if it doesn't find a VI-a already running?  Any ideas on why it's opening a new VI instead of reusing the one in memory.  Is there a setting somewhere that would explain why this happens on the test machine and not my development machine.
  I'm currently trying to control a VI from c++ using the ActiveX server on the VI in LabVIEW 9, I'm building the application using MS VC++ express 2010.  This VI(lets call it VI-a is invoke node to get and set data on another VI-b.  For testing I have a copy of VI-b that is gutted so it loads into memory but doesn't run, it connects to hardware I don't have in my development setup.
#import "PATH\LaVIEW.tlb" 
static LabVIEW::_ApplicationPtr         pLVApp = (LabVIEW::_ApplicationPtr)      NULL;
static LabVIEW::VirtualInstrumentPtr    pVI    = (LabVIEW::VirtualInstrumentPtr) NULL; 
void init_VI()
    //Multithreaded application
    CoInitializeEx(NULL, COINIT_MULTITHREADED); 
    pLVApp.CreateInstance("LabVIEW.Application"); 
    //Error checking not shown
    return; 
void connect_to_fp()
    HRESULT            hr                      = S_OK;
    char                    password[60]    = "";
    VARIANT_BOOL  reserveForCall  = VARIANT_FALSE;
    long                    options             = 0x20;
    //Multithreaded application
    CoInitializeEx(NULL, COINIT_MULTITHREADED);  
    pVI.CreateInstance("LabVIEW.VirtualInstrument");
    pVI = pLVApp->GetVIReference(vi_path, LPCTSTR(password), reserveForCall, options); 
    //Error checking not shown
    hr = pVI->OpenFrontPanel(VARIANT_TRUE, LabVIEW::eVisible)
    return; 
I wasn't able to try commenting out the CreateInstance call on the test machine.  However removing it has had no effect on my development machine.
Details of my setup: 
  On my development machine I can run VI-a before starting the c++ application and it will connect and use the VI-a that is already running in memory or I can let the c++ application bring up VI-a.  When I was running a test recently when I would get the reference to VI-a it would open a new FP for VI-a (I'm assuming it started a new instance of VI-a) instead of using the one that was currently loaded and running, the VI-a also isn't running like it normally does.  The VI-a gets it's values from VI-b once at init but it never updates them again.  Also there is a switch on VI-a that controls a status indicator that doesn't update when the switch when it is toggled.  There is another indicator on a separate tab that shows how long a loop took to execute that is changing, which is why I believe it is at least partially running.
 My biggest issue is that I haven't been able to recreate this on my development machine.  Anytime I have VI-a open and running my c++ application reuses that one instead of trying to open a new one.  My connection code is pretty much strait out of the c++/ActiveX example from NI. 
Thanks. 
Solved!
Go to Solution.

Answer 1

I haven't found an answer to erroring out instead of creating a new instance but I did find a way to deal with the project issue.  If you create an instance, then open the project, then open the VI from the projects instance it will work.  New init_VI:
 void init_VI()
    //Multithreaded application
    CoInitializeEx(NULL, COINIT_MULTITHREADED); 
    pLVMainApp.CreateInstance("LabVIEW.Application"); 
   pLVPrj = pLVMainApp->OpenProject(PATH_TO_PROJECT); 
    pLVApp = pLVPrj->GetApplication();
    //Error checking not shown
    return;