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Call VB ActiveX dll from C language

Posted on 2004-04-06
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Last Modified: 2012-06-22
The scenario is simple - a screen displays a list of data. Click an item on the list to display an scanned image. A document id is passed to determine which image to display. IBM imaging software displays the image.

Problem is: IBM imaging software uses ActiveX VB dll to display image and screen is written in J. D. Edwards which is a low level C language, so I must call the VB dll from C language. I'm using MS Studio 6. I wonder if this is possible?????

I have the following so far. When I click the screen, it goes through the program and does nothing. I have tried to debug this by adding some dll's into the Program Settings with no success. A window pops up showing the Disassembly, breakpoints are not recognized and I can't display any field values.

Any help is very much appreciated ... Jim

// code from header

#include <windows.h>
typedef (*PFNJDE2CM)( LPCSTR ); // VB dll to call receives one string parm

#ifndef DATASTRUCTURE_D550413M
#define DATASTRUCTURE_D550413M

typedef struct tagDSD550413M
{
  char              szDOCNAME[9];      // string parm is passed into this header
} DSD550413M, *LPDSD550413M;  // and stored in this struct

#define IDERRszDOCNAME_2                          1L

#endif

......
// code from .c
#define B550413M_c
#include <B550413M.h>   // this is header above

{
   int nResult = 0;
   PFNJDE2CM lpJDE2CM;
   HINSTANCE hLibrary;

   hLibrary = LoadLibrary("c:\\JDE2CM.dll.dll"); // this is VB dll

   if(hLibrary != NULL)
   {
        // gets the address of the function inside the VB dll
        lpJDE2CM = (PFNJDE2CM) GetProcAddress (hLibrary, "DllGetClassObject");

            if(!lpJDE2CM)
      FreeLibrary(hLibrary);
            else
           {
               // call the VB dll function
                const char *docid = 0;          
      docid = lpDS->szDOCNAME;    
      nResult = lpJDE2CM(docid);    
           }
}

   return (ER_SUCCESS);
}

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Question by:jimjung27
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by:Droby10
ID: 10766343
i've never done this, but i would suggest maybe disassembling a vb written exe that makes use of the same dll.  the reason being i bet there is a bootstrap of sorts that centers around the msvbxxx.dll runtime, and _perhaps_ even plays a role in providing a layer of com dispatching.  i'm not certain of either of those things, but they sound logical at the surface level.

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Expert Comment

by:ankuratvb
ID: 10766422
Just do a google on 'call vb activex dll c language' in google groups.

U'll get plenty of similar links.
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Author Comment

by:jimjung27
ID: 10777626
I'm still alive but dying to get rid of the 250 points...

I've written 2 cpp wrappers using some of the info from the links - thanks for the tip.

One of them disassembles the VB code and one imports the VB code. One is an exe and one is a dll.

They both only compile if an unsigned short** datatype is passed to the VB function, but the function actually receives a string (coded in the VB function). Why is this?

The only other problem I have is I get a link error:

LNK4098: defaultlib "msvcrt.lib" conflicts with use of other libs; use /NODEFAULTLIB:library

When I try to go into the MS Studio Project Settings, the Link tab is missing??? I think this may be because of the J.D.Edwards not accepting any of the cpp code or settings. Id their a manual way to run the link from DOS?
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Expert Comment

by:ankuratvb
ID: 10780185
See this:

http://www-unix.mcs.anl.gov/mpi/mpich/docs/mpichntman/node10.htm

It shows how to compile in VC++ from the command line.
It should solve ur problem.

U can explicitly call the link.exe and give the /NODEFAULTLIB option there.
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