c# - An attempt was made to load a program with an incorrect format -

i using c# loading c++ dll, , got error:

"an unhandled exception of type 'system.badimageformatexception' occurred in myapp.exe" "additional information: attempt made load program incorrect format. (exception hresult: 0x8057000b)

i not figure out why. c++ dll generated using vs2012 wizard, win32 application, dll pre-head. built x64 option. here code:

// mynativedll.cpp : defines exported functions dll application. //  #include "stdafx.h"     //char* pmemorybuffer = null;     using namespace std;      __declspec(dllexport) long  test()     {         long a;          = 1;          a++;          return a;     } 

the c# code calling is:

[dllimport("c:\\mynativedll\\x64\\debug\\mynativedll.dll",  entrypoint = "test")] private extern static int test(); void dojob() {    long = test();  // exception thrown here } 

c# code built cpu option, , loading x64 native dll. wondering did wrong? have been trying long, stuck here. thanks!

update when compile native dll using win 32 option, , set correct dll path, loads successfully. when compile native dll x64 options, load correct path, loading fails.

as mentioned: the c++ dll generated using vs2012 wizard, win32 application, dll pre-head. built x64 option

the dll , exe have both 32 bit, or both 64 bit.