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

namespace LazyExamp
{
    class Program
    {
        static void Main(string[] args)
        {
            //1   
            Lazy<int> lazy = new Lazy<int>(() => { Console.WriteLine("hello"); return 42; });
            Console.WriteLine(lazy.Value);
             //2
            int a = 5, b = 20;
            var laz = Lazy.New(() => { Console.WriteLine("Hello2"); return new { Mul = a * b, Sum = a + b }; });
            Console.WriteLine("{0},{1}", laz.Value.Mul, laz.Value.Sum);
        }
    }
    public static class Lazy
    {
      public static Lazy<T> New<T>(Func<T> func)
        {
            return new Lazy<T>(func);
        }
    }
    public class Lazy<T>
    {
        private Func<T> func;
        private T result;
        private bool hasValue;
             public Lazy(Func<T> func)
        {
            this.func = func;
            this.hasValue = false;
        }
        
         public T Value
        {
            get
            {
                if (!this.hasValue)
                {
                    this.result = this.func();
                    this.hasValue = true;
                }
                return this.result;
            }
        }
    }
}