ASP.NET泛型四之使用Lazy<T>实现延迟加载

public class LazySinleton
{
    private LazySingleton()
    {}
 
    public static LazySingleton Instance
    {
        get
        {
            return Lazy.data;
        }
    }
 
    private class Lazy
    {
        static Lazy()
        {}
 
        internal static readonly LazySingleton data = new LazySingleton();
    }
}

public class Lazy<T>
{
    public Lazy();
    public Lazy(bool isThreadSafe);
    public Lazy(Func<T> valueFactory);
    public Lazy(LazyThreadSafeMode mode);
    public Lazy(Func<T> valueFactory, bool isThreadSafe);
    public Lazy(Funct<T> valueFactory, LazyThreadSafetyMode mode);

    public bool IsValueCreated{get;}
    public T Value {get;}
    public override string ToStirng();
}

public class SomeClass
{
    public int ID{get;set;}
}

Lazy<SomeClass> temp = new Lazy<SomeClass>();
Console.WriteLine(temp.Value.ID);

pubic class SomeClass
{
    public int ID{get;set;}
    public SomeClass(int id)
    {
        this.ID = id;
    }
}

Lazy<SomeClass> temp = new Lazy<SomeClass>(() => new Big(100));
Console.WriteLine(temp.Value.ID);

    public class MyLazy<T>
    {
        private volatile object boxed; //volatile说明在多线程状况下，也可以修改该字段
        private Func<T> valueFactory; //委托，用来生产T对象实例

        static MyLazy(){}
        public MyLazy(){}

        public MyLazy(Func<T> valueFactory)
        {
            this.valueFactory = valueFactory;
        }

        public T Value
        {
            get
            {
                Boxed boxed = null;
                if (this.boxed != null)
                {
                    boxed = this.boxed as Boxed;
                    if (boxed != null)
                    {
                        return boxed.value;
                    }
                }
                return this.Init();
            }
        }

        //初始化对象实例
        private T Init()
        {
            Boxed boxed = null;
            if (this.boxed == null)
            {
                boxed = this.CreateValue();
                this.boxed = boxed;
            }
            return boxed.value;
        }

        //创建内部类实例
        private Boxed CreateValue()
        {
            //如果创建对象实例的委托valueFactory存在
            if (this.valueFactory != null)
            {
                //就通过委托生成对象实例
                return new Boxed(this.valueFactory());
            }
            else
            {
                //否则，通过反射生成对象实例
                return new Boxed((T)Activator.CreateInstance(typeof(T)));
            }
        }

        //内部嵌套类，通过构造函数对其字段赋值
        private class Boxed
        {
            internal T value;
            internal Boxed(T value)
            {
                this.value = value;
            }
        }
    }

    public class Big
    {
        public int ID { get; set; }
        public Big(int id)
        {
            this.ID = id;
        }
    }

    public class BigFactory
    {
        public static Big Build()
        {
            return new Big(10);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            MyLazy<Big> temp = new MyLazy<Big>(() => BigFactory.Build());
            Console.WriteLine(temp.Value.ID);
            Console.ReadKey();
        }
    }