Unable to find an entry point when calling C++ dll in C#

Question

I am trying to learn P/Invoke, so I created a simple dll in C++

KingFucs.h:

namespace KingFuncs
{
    class KingFuncs
    {
    public:
        stati         


        

Answer 1

You need to use extern "C" when you export your function so that you suppress C++ name mangling. And you also should not try to p/invoke to members of a class. Use free functions instead:

extern "C" {
    __declspec(dllexport) int GiveMeNumber(int i)
    {
        return i;
    }
}

On the managed side your DllImport attribute is all wrong. Don't use SetLastError which is for Win32 APIs only. Don't bother setting CharSet if there are not text parameters. No need for ExactSpelling. And the calling convention is presumably Cdecl.

[DllImport("KingFuncDll.dll", CallingConvention=CallingConvention.Cdecl)]
public static extern int GiveMeNumber(int i);