DLL HELP

[delali]

I am a summer intern and I have a few questions on my summer project.

I have some VC++ code that I would like to be able to call in VB.NET. What I am attempting to do is while the VC++ code is running I would like to periodically extract some data to be plotted and viewed in a VB interface. I am not sure what that best means of approach is for this. People have given many suggestions, but as I have never interfaced VB and VC before I am getting a little confused and am not sure what advice to listen too.

It was suggested to me that I could create a DLL with the VC++ code that would be called in VB, but in my research and in all of the examples that I have seen it seems as though a DLL is used to call functions from different programs, is this true? Will I be able to have the VC++ code running and extract data if I create a DLL?

It was also suggested that I use the LoadLibrary function, but I am not sure exactly what that is used for or how to use it.

I appreciate any help that anyone can give me, to help steer me in the correction direction.


Thanks!
Delali Dzirasa
PS I don’t know if this is needed but I am running on W2K, and VC++ 6.0, where the current application is compiled as an EXE console application.

 

[wduty]

Is the c++ program something that needs to run independently of the vb interface?

 

[delali]

No it does not, currently the EXE is in VC++ in a console app, I do not need to see that, but as it gathers/manipulates data I would like to be able to capture that data in real time to be displayed in VB.


Delali

 

[wduty]

Well, not needing to see the console does not mean that the program does not need to run independently of the VB interface.

When you say things like "as it gathers/manipulates data", it sounds like the C++ program needs to remain running "in the background" even when you close the VB interface.

Is that the case?

 

[delali]

>When you say things like "as it gathers/manipulates data", >it sounds like the C++ program needs to remain running "in >the background" even when you close the VB interface.

>Is that the case?

No, that is not the case I will have a button that starts/launches the C++ code from VB then I will have a button that close it from VB.

Delali

 

[wduty]

Ok, so you could do a dll. Apparently VB can load dlls. Instead of "LoadLibrary" which is the C/++ function call to load a dll, you use "Declare" and "Lib". I looked around for a minute and there seem to be a lot of links which deal with this topic. Here's one:

http://www.codeguru.com/dll/vbString.shtml

I think everything you need (in principle) is covered there. Thing is, you have to understand enough C++ to take your console app code and make a dll out of it (especially since it sounds like there's some state maintenance and threading going on). If you don't, then you need to get up to speed on writing a basic dll. (try Petzold's "Programming Windows" chapter 21).

Good luck.

 

[RahulGade]

Why you people are discussing over these things, just use ALT-COM wizard in VC++6 to generate a COM Based DLL. Then in your VB application you can add the dll as a reference and used any functionality.

Rahul If you think you can't do it,You will never be able to do it.

 

[delali]

Thanks, I will read up on the COM based DLL and give it a try...thanks again for the input!

Delali

 

[wduty]

RahulGade:

Sure. ATL away! I was just following his lead out of curiosity.

Keep in mind however, if you do a COM object you gotta register it on any other machine than the one you built it on (ask people to do regsvr32 or give them a batch file).