C++ and C# p/invoke Not Working Cannot Start Creo And Throws AccessViolationException

Hi all,

I'm using Creo Parametric 7.0.2.

I'm working on trying to use C# p/invoke interop method to call a Creo function from the C++ toolkit. 

I have a C++ .exe that will include the Creo async functionality. 

It exposes these two functions:

extern "C" __declspec(dllexport) int ConnectToCreo()
{
	pfcAsyncConnection_ptr connection = pfcAsyncConnection::Start("C:\\Program Files\\PTC\\Creo 7.0.2.0\\Parametric\\bin\\parametric.exe", NULL);
	return 0;
}

extern "C" __declspec(dllexport) int NoCreo()
{
	return -1;
}

For the C# side, I created a simple command line app:

using System.Runtime.InteropServices;

namespace CreoInteropPoC;

internal class Program
{
 [DllImport("CreoAsync.exe", CallingConvention = CallingConvention.Cdecl)]
 public static extern int ConnectToCreo();

 [DllImport("CreoAsyncDll.exe")]
 private static extern int NoCreo();

 static void Main(string[] args)
 {
 Console.WriteLine(NoCreo());
 ConnectToCreo();
 Console.ReadKey();
 }
}

The C# app calls the function NoCreo and works fine but throws an AccessViolationException when calling ConnectToCreo.

I have also attached a screenshot of the call stack. 

Is it possible to use p/invoke to call Creo functions? Can you point me to what I'm doing wrong?