Question

In my dll there is a method that I want to export.

//Works:

extern "C" __declspec(dllexport)

//Wont work

__declspec(dllexport)

C++ Export:

 extern "C" __declspec(dllexport) int Test();

C# import:

[DllImport("CircleGPU2_32.DLL", EntryPoint = "Test", 
    CallingConvention = CallingConvention.StdCall)]
public static extern int Test();

Why I need the extern “C” ?

Answer 1

The main reason is to prevent the C++ name mangler from mangling the name of the function.

Try exporting it without the extern "C" and inspect the resulting DLL in Dependency Walker and you will see a quite different name for the exported function.