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 :)

Community · Accepted Answer · 2017-05-23 12:29:16Z

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, 2017 at 12:29

CommunityBot

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answered Jan 16, 2014 at 11:36

Spook

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3 Comments

marsh-wiggle Over a year ago

Sry, spook, my demo code was incomplete, i corrected it. In the original it is defined correctly. I corrected my question now.

Spook Over a year ago

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".

marsh-wiggle Over a year ago

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!

Spook · Accepted Answer · 2014-01-16 12:13:41Z

2

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()

edited Jan 16, 2014 at 12:13

Spook

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answered Jan 16, 2014 at 12:02

vathsa

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