How to use DLL C++ (VB) in C ?

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I wrote this code in an example.
I wrote this code in Visual Basic C++. Now I want to call it in C.
I want to get 20 in C.
Can you guide?
thanks.
I created this Dll in C++ :

What I have tried:

extern "C" __declspec(dllexport) int number(int a); 
int DllMain()
{
    a=20;        
    return (a);
}

Posted 15-Dec-18 23:45pm

Member 14061434

Updated 16-Dec-18 6:43am

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OriginalGriff · Answer 1 · 2018-12-16T00:48:00

If you are genuinely using Visual Basic, then "not at all easily".
First off, Visual Basic has nothing at all to d with C++ - it's a managed .NET language, which means you need the appropriate .NET framework installed and loaded on the machine in order to use it.

C is not managed, it's native - it knows nothing at all about .NET - so it gets very complicated: Calling C# from C - Stack Overflow[^] (C# is another .NET language, and it's exactly the same procedure for VB).

If you want to call native C++ functions from C, that's easier: Mixing C and C++ Code in the Same Program[^]
Just don;t use the term "Visual Basic" again - it's nothing to do with C or C++!

Richard MacCutchan · Answer 2 · 2018-12-16T02:05:00

Solution 2

You cannot use it in any language unless you provide a proper interface. DllMain is called by Windows when the library is first loaded, it is not a user function. See Creating and Using a Dynamic Link Library (C++) | Microsoft Docs[^].

Also there is no such thing as Visual Basic C++.

Posted 16-Dec-18 2:05am

Richard MacCutchan

KarstenK · Answer 3 · 2018-12-16T06:43:00

The code that you wrote has a main flaw by declaring the number function, but implementing the the main. Write the declaration in the header and the implementation in the c-file.

It MUST have the same signature as declared. So:

C++

int number(int a)
{
    a=20;        
    return (a);
}

Calling dlls via GetProcAdress is very easy, But take care on the signature and every error.

How to use DLL C++ (VB) in C ?

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