class Program
    {
        static void Main(string[] args)
        {
            List<entityA> source = new List<entityA>();
            for (int i = 0; i < 20; i++)
            {
                source.Add(new entityA
                {
                    name = "悟空" + i,
                    sex 
 
= i % 2 == 0 ? "男" : "女",
                    age = i
                });
            }

            Stopwatch Watch3 = new Stopwatch();
            Watch3.Start();
            loop2(source);
            Watch3.Stop();
            Console.WriteLine("一般foreach迴圈耗時：" + Watch3.ElapsedMilliseconds);
            

            Stopwatch Watch5 
 
= new Stopwatch();
            Watch5.Start();
            loop4(source);
            Watch5.Stop();
            Console.WriteLine("並行foreach迴圈耗時：" + Watch5.ElapsedMilliseconds);
            Console.ReadLine();
        }

        //普通的foreach迴圈
        static void loop2(List<entityA> source)
        {
            
 
foreach (entityA item in source)
            {
                item.age = +10;
                System.Threading.Thread.Sleep(3);//毫秒
            }
        }

        //並行的foreach迴圈
        static void loop4(List<entityA> source)
        {
            Parallel.ForEach(source,new ParallelOptions { MaxDegreeOfParallelism=Environment.ProcessorCount}, item =>
            {
                item.age = item.age + 10;
                System.Threading.Thread.Sleep(3);
            });
        }
        //                  0   1   2    5   10   100   500    10000  10000    Environment.ProcessorCount*4 10000    Environment.ProcessorCount*2
        //一般foreach迴圈耗時 0   38  58   119 218  2011  10000  20010  20010                                 20008
        //並行foreach迴圈耗時 97  84  65   68  92   564   2500   5080   4055                                  4087

    }
    //簡單的實體
    class entityA
    {
        public string name { set; get; }
        public string sex { set; get; }
        public int age { set; get; }
    }

2毫秒以上可以用並行