May build, but won't compile

//These codes will build but will not compile. I hope someone would know
why; and tell me.

//I got the below error message during compile time

#include "stdafx.h"

#include <string.h>

#include <string>

#using <mscorlib.dll>

#include <tchar.h>

using namespace System;

using namespace std;

__gc class Month

{

public:

Month(int, int); // provide a default value (4 here) if you want

int getDayOfWeek () {return dayOfWeek;}; //line 17
<----------------------------------X

private:

int dayOfWeek ; // This must be initialized with a constant

int weekOfMonth ;

int pDaysOfMonth __gc [,];

};

int _tmain()

{

Month *March;

Console::Write(March->getDayOfWeek()); // line 31
<-----------------------------------X

return 0;

}

/***********************************************/

Month::Month(int val1,int val2)

{

Console::Write(S"The default constructor is called\n");

weekOfMonth = val1;

dayOfWeek = val2;

pDaysOfMonth = new int __gc[weekOfMonth,dayOfWeek];

}

/*

Unhandled Exception: System.NullReferenceException: Object reference not set
to

an instance of an object.

at line 17

at main() line 31

*/