Working with objects in array-need help

 using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;

namespace WindowsFormsApplication3
{
    static class Program
    {
        /// 

        /// The main entry point for the application.
        /// 

        [STAThread]
        static void Main()
        {
            Student std = new Student();
            std.Grades = new Grade[3];

            Console.WriteLine("Std Grade for Math");
            string _grade = Console.ReadLine();
            std.Grades[0] = new Grade();
            std.Grades[0].StdGrad = int.Parse(_grade);

            Console.WriteLine("Std Grade :" + std.Grades[0].StdGrad);
            Console.ReadLine();

        }

        public class Student
        {
            public Grade[] Grades { get; set; }
        }

        public class Grade
        {
            public int StdGrad { get; set; }
        }
    }
}