Using NullCoalesce Operator

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace TestConsoleApp
{
    class NullCoalesce
    {
        static int? GetNullableInt()
        {
            return null;
        }

        static string GetStringValue()
        {
            return null;
        }

        static DateTime? GetDateTime()
        {
            return null;
        }

        static void Main()
        {
            int? x = null;

            // Set y to the value of x if x is NOT null; otherwise,
            // if x = null, set y to -1.
            int y = x ?? -1;

            // Assign i to return value of the method if the method's result
            // is NOT null; otherwise, if the result is null, set i to the
            // default value of int.
            int i = GetNullableInt() ?? default(int);

            Console.WriteLine("i = " + i);

            string s = GetStringValue();

            // Display the value of s if s is NOT null; otherwise,
            // display the string "Unspecified".
            Console.WriteLine(s ?? "Unspecified");

            DateTime? dt = new DateTime();

            object obj = (object)dt ?? DBNull.Value;
            Console.WriteLine(obj == null ? "null" : "not null");
        }
    }
}