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Loading C++ DLL In Visual Basic
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Submitted on: 11/17/2009 9:01:56 AM
By: Andron Smith
Level: Beginner
User Rating: Unrated
Compatibility:VB 6.0
Users have accessed this code 2598 times.
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(About the author) |
| | | Well i have been studying combining C++ with Visual Basic. See C++ offers power while Visual Basic offers Rapid Development. The Limitations Visual Basic may have can be over taken with a bit of help from C++. With that said, I introduce to you my attempt at CPP with Visual BAsic programming. After some research and studying of using the DLL with vb, i've put it to code base on my understanding. Now The first two functions will work. but you must compile the program, leave the DLLs in the Debug folder CPP would provide. The Program fails on MultiplyAll on my System, maybe it might do better on yours but being a programmer, real programmers never let anything beat us so i will try to figure out why multiplyall is recieving error and i will reupload the corrected.. Thanks. Experiment with the code, use my comments section for any discussion you wish to have on CPP DLL and VB.
TECH NOTES UPDATE:
Tech notes and Findings:
Well since the post. I have done some more practices on it. As a result i've found, that visual C++ does actually passes the arguments, this is tested when i called a MessageBox from out of the C++ DLL. Notice, that prior to the Bad Dll Calling Prevention you would get an email listing the data you sent. This is because the DLL is recieving the data, it is compatible with the data being sent to it. i used how ever LPSTR for the data type giving and passed. Now the problem comes when it returns a value back to the DLL. For some reason visual basic, is reading our Function as a Sub Routine so it's like it's expecting us to be calling a sub routine. This is tested when i created a TellUser function in C++. I noticed the function was void. returned no value but instead of calling it as a sub routine i called it as a function and as a result i recieve similiar error however when i called it as a sub routine it recieved no error. So i will study and dive deeper into this.
Also i have also found that Dev C++ allows full DLL calling. in that i used the following
extern "C" __declspec(dllexport) __stdcall LPSTR MessageMe(LPSTR message);
from the function i made it send a message box containing the message. Through my studies on it, i've realize DevC++ does not like the .def declaration. but how ever it listed the function and called with out an error visual basic.
my attempt to use the similiar line in visual c++ failed prompting me to believe that C++ does not like DevC++ calling methods where as DevC++ does not like C++ calling methods.
Norm Cook, i try and experiment with your suggestion, believe me you will read the results here in the future posting.
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Other 38 submission(s) by this author
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 Report Bad Submission | | | | | Your Vote! | |
See Voting Log | | | | Other User Comments |  11/13/2009 4:32:02 AM: Lefteris Eleftheriades
Thank you, I never knew about the .def files, I always exported with __declspec(dllexport) and I got wierd exportnames for my functions
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| 11/13/2009 1:08:19 PM: Bob Hutchison
MultiplyAll fails on my system as well (XP-SP2). Being a real noob at C++, I'll let the experts figure it out <G>
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| 11/14/2009 11:46:12 AM: Andron Smith
Well, let's look at it real quickly. In the other functions declared in visual basic, neither of them asked for parameters to be passed. Where as multiplyAll is asking for a parameter. So here the error is exporting a function that requires a parameter to be passed. i also have a passion for software engineering so i like to study my coding. on one hand maybe the parameters i'm attempting to pass in C++ to visual basic is not compatible with visual basic. I mean maybe they have a certain datatype that replaces the INT. But then again, visual basic accepts a return in the same type. Confusing? I know. it's just trying to study it and learn a bit more about Importing C++ functions into Visual Basic that requires Parameters.
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| 11/14/2009 1:34:42 PM: Norm Cook
VB6 expects C++ dll routines to use
__stdcall vice __declspec. Note that the routine that fails has two arguments, so __declspec reverses them in your call.
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