64 bit migration __declspec(dllexport) Function Call Crash

Question

I have a DLL which has C++ functions (sample below) and C# managed code. It is build using /clr option.
When C++ extern function is called from executable (x86 32 bit build) eveyrthing works as desired. But in 64 bit build it crashes on function call.
Used
dependecy walker to verify all dependencies.
First-chance exception at 0x000007fefde9940d in XXXXX.exe: 0x04242420: 0x4242420.
// DLL Build with CPPDLL_EXPORT and /clr
// Header File
#ifdef CPPDLL_EXPORT
#define CPPDLL_API __declspec(dllexport)
#else
#define CPPDLL_API __declspec(dllimport)
#endif
extern "C" {
CPPDLL_API void TestCheckVersion();
// In Executable
// call to
TestCheckVersion(); // crash at this point.

Answer 1

Probably you are not using [DllImport] attribute correctly. Show the details about the C# part.
Since the DLL is built wit /clr option, then a different approach is possible: create a managed class like this:
public ref class MyClass
public:
    static void Test()
It does not require __declspec.
In C#, add a reference to DLL, then call the function:
“MyClass.Test()”. If it works, then add more code to Test, such as
TestCheckVersion().