c主要后的类声明？

#include "stdafx.h"
using namespace System;

class Calculater; // how to tell the compiler that the class is down there? 

int main(array<System::String ^> ^args)
{
    ::Calculater *calculater = new Calculater();

    return 0;
}

class Calculater
{
public:
    Calculater()
    {
    }
    ~Calculater()
    {
    }

};

我在主要之后声明了这个类,我怎么告诉编译器我的类是什么？我试过了
class Calculater;在主要之前但它不起作用.