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
     
       skill;        public SpecialSkill Skill        {            get { return skill.Value; }        }        public Hero(string name)        {            Name = name;            FullName = "Super " + name;            skill = new Lazy
      
       (() => 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