Linq序列不包含任何元素解决方法

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

namespace ConsoleApplication1
{
    class User
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public DateTime Created { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            List<User> Users = new List<User>();

            User user = Users.First();
            if (user != null)
                Console.WriteLine(user.Name);

            Console.ReadKey();
        }
    }
}

User user = Users.FirstOrDefault();