How to call from C# simple function in C++ DLL

Question

i have a simple function in c++ (not a method of a class)

__declspec(dllexport) extern "C" void __stdcall TestFunc();

i try to call it from c#:

[DllImport("ImportTest.dll")]  
public static extern void TestFunc();  

...  

TestFunc();

It throws an "entry point could't be found" exception.

Whats wrong?

Thank you for helping me :)

score 5 · Accepted Answer · edited May 23 '17 at 12:29

5

Try (guessing, that DLL is written in VS)

extern "C" __declspec(dllexport) void __stdcall TestFunc();

That's:

__declspec(dllexport) to notify compiler, that this function is to be exported from the DLL;
extern "C" mainly to prevent function name decorations;
__stdcall, because this is default calling convention if you specify none in [DllImport] directive.

In the future, you can check if your function is exported from DLL using Dll export viewer.

edited May 23 '17 at 12:29

Community

1
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answered Jan 16 '14 at 11:36

Spook

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Sry, spook, my demo code was incomplete, i corrected it. In the original it is defined correctly. I corrected my question now. – marsh-wiggle Jan 16 '14 at 11:49
Have you actually used `Dll export viewer` to check, what is the name of your exported function? If .NET can not find the entry point it means, that it can not find specified function name in DLL export list. I bet, that VS decorated name of your function despite `extern "C"`. – Spook Jan 16 '14 at 12:12
In the original DLL Export Viewer didn't show any exported function. Changing it to "extern "C" _declspec(dllexport) void TestFunc();" the function is shown. Great tool! Thx for your help! – marsh-wiggle Jan 16 '14 at 12:16

score 2 · Answer 2 · edited Jan 16 '14 at 12:13

In C++ function , at header(if your function is declared in header) add

extern "C" _declspec(dllexport) void TestFunc();

at the function definition use

_declspec(dllexport) void TestFunc()
{

}

At C# side,you need to declare a function like

[DllImport(@"ImportTest.dll",
                 EntryPoint = "TestFunc",
                 ExactSpelling = false,
                 CallingConvention = CallingConvention.Cdecl)]
            static extern void NewTestFunc()

Now use , NewTestFunc()

How to call from C# simple function in C++ DLL

2 Answers2