可空类型

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Nullable;
namespace 可空类型
{
    class Program
    {
        static void Display(Nullable<int> x)
        {
            Console.WriteLine("HasValue:{0}", x.HasValue);
            if(x.HasValue)
            {
                Console.WriteLine("Value:{0}",x.Value);
                Console.WriteLine("Explicit conversion: {0}",(int)x);
            }
            Console.WriteLine("GetValueOrDefault():{0}", x.GetValueOrDefault());
            Console.WriteLine("GetValueOrDefault(10):{0}", x.GetValueOrDefault(10));
            Console.WriteLine("ToString():{0}", x.ToString());
            Console.WriteLine("GetHashCode():{0}", x.GetHashCode());
            Console.WriteLine();

        }
        static void Main(string[] args)
        {
            Nullable<int> x = 5;
            x = new Nullable<int>(5);
            Console.WriteLine("Instance with value");
            Display(x);
            x = new Nullable<int>();
            Console.WriteLine("Instance without value");
            Display(x);
            Console.ReadKey();

        }
    }
}