延迟加载

延迟加载：数据赋予一个对象时不加载数据，当 .tolist 时进行加载数据，节省性能

实例

  public class Hero
    {
        public string FullName { get; set; }
        public string Name { get; set; }

        private readonly Lazy<SpecialSkill> skill;
        public SpecialSkill Skill
        {
            get { return skill.Value; }
        }

        public Hero(string name)
        {
            Name = name;
            FullName = "Super " + name;

            skill = new Lazy<SpecialSkill>(() => new SpecialSkill(name));
        }
    }

    public class SpecialSkill
    {
        public int Power { get; set; }
        public string SkillName { get; set; }
        public int StrengthSpent { get; set; }
        public SpecialSkill(string name)
        {
            Console.WriteLine("loading special skill .....");
            Power = name.Length;
            StrengthSpent = name.Length * 3;
            SkillName = name + " Blazing";
            Console.WriteLine(SkillName + ",... this's what makes a legend!");
        }
    }

当不需要加载  specialskill时，就不加载