Getting a System Entry Exception

#include<iostream>
using namespace std;


class __declspec(dllexport) Hello
{
public:	
	int PrintHello(char* str);
};

#include<iostream>
#include "Hello.h"
using namespace std;

int Hello::PrintHello(char* str)
{
    cout<<"Hello "<< str <<endl;
    return 0;
}

#include<iostream>
#include"Hello.h"
__declspec(dllexport) Hello* APICreateHello();
__declspec(dllexport) void APIDestroyHello();

#include<iostream>
#include "API.h"

extern "C" __declspec(dllexport)  Hello*  __cdecl APICreateHello(char* str)
{
    return new Hello();
}
extern "C" __declspec(dllexport)  void   APIDestroyHello(Hello* obj)
{
        delete obj;
}

public class MyCustomDLLWrapper
{
    // extern "C" MYCUSTOMDLL_API int AddNumbers(int x, int y);
    [DllImport("TestLib.dll",EntryPoint = "APICreateHello")]
    public static extern IntPtr APICreateHello(string str);
}
namespace TestManagedApp
{
    class Program
    {        public static int Main(string[] args)
        {
            IntPtr x = MyCustomDLLWrapper.APICreateHello("Pavan");


            return 0;
        }
    }
}