Mixing Managed and Unmanaged code

// This is the main project file for VC++ application project 
// generated using an Application Wizard.

#pragma unmanaged

#include "Windows.h"

class CUnmanagedClass
{
public:
	void ShowMessageBox(char* szMessage)
	{
		::MessageBox(NULL, szMessage , "CUnmanagedClass", MB_OK);
	}
};

#pragma managed

#using <mscorlib.dll>

using namespace System;
using namespace System::Runtime::InteropServices;


__gc class CManagedClass
{
public:
	void ShowMessage(System::String* strMessage)
	{
		System::Console::WriteLine(strMessage);
	}
};

int main(void) 
{
	String* strMessage = S"Hello world";

	CManagedClass* pCManagedClass = new CManagedClass();
	pCManagedClass->ShowMessage(strMessage);

	char* szMessage = (char*)Marshal::StringToHGlobalAnsi(strMessage);
	CUnmanagedClass cUnmanagedClass; cUnmanagedClass.ShowMessageBox(szMessage);
	Marshal::FreeHGlobal((int)szMessage);

    return 0;
}