VM off: 300k keys, 4096 bytes values: 1.3G used
VM on: 300k keys, 4096 bytes values: 73M used
VM off: 1 million keys, 256 bytes values: 430.12M used
VM on: 1 million keys, 256 bytes values: 160.09M used
VM on: 1 million keys, values as large as you want, still: 160.09M used 

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

namespace 正确打开方式
{
    class Program
    {
        public static async void Excute()
        {
            Console.WriteLine(Thread.CurrentThread.GetHashCode() + " 开始 Excute " + DateTime.Now);
            var waitTask = AsyncTestRun(); //表示一个可以返回值的异步操作。
            waitTask.Start();
            //int i = 0;
            int i = await waitTask;
            Console.WriteLine(Thread.CurrentThread.GetHashCode() + " i " + i);
            Console.WriteLine(Thread.CurrentThread.GetHashCode() + " 结束 Excute " + DateTime.Now);
            Console.ReadKey();
        }
        public static Task<int> AsyncTestRun()
        {
            Task<int> t = new Task<int>(() =>
            {
                Console.WriteLine(Thread.CurrentThread.GetHashCode() + " Run1 " + DateTime.Now);
                Thread.Sleep();
                ;
            });
            return t;
        }

        public static async Task<int> AsyncTest()
        {
            Task.Run(() =>       //将在线程池上运行的指定工作排队，并返回该工作的任务句柄。
            {//创建了新线程
                Console.WriteLine(Thread.CurrentThread.GetHashCode() + " Run1 " + DateTime.Now);
                Thread.Sleep();
            }).GetAwaiter().GetResult();
            ;
        }
        static void Main(string[] args)   //错误    1    “正确打开方式.Program.Main(string[])”: 入口点不能用“async”修饰符标记
        {
            Console.WriteLine(Thread.CurrentThread.GetHashCode() + " 开始 Excute " + DateTime.Now);
            //AsyncTest();   //正常调用不会创线程
            //AsyncTest();  //出现三行 说明 创建了 一个线程 、、出现四行 说明 创建了 两个个线程  五行
            //但是，好像await AsyncTest();还是没启作用。没错，事实就是，他真的不会起作用。。。
            //Excute();

            Console.WriteLine("--");
            Console.WriteLine("--");

            //Excute2();
            Excute3();
            Console.ReadKey();
        }

        public static async void Excute2()
        {
            Console.WriteLine(Thread.CurrentThread.GetHashCode() + " 开始 Excute2 " + DateTime.Now);
            await SingleAwait();    //等待线程结束 然后执行后面的
            Console.WriteLine(Thread.CurrentThread.GetHashCode() + " 结束 Excute2 " + DateTime.Now);
        }

        public static async Task SingleAwait()
        {
            Console.WriteLine(Thread.CurrentThread.GetHashCode() + " AwaitTest开始 " + DateTime.Now);
            await Task.Run(() =>   //await  等待线程完成
            {
                Console.WriteLine(Thread.CurrentThread.GetHashCode() + " Run1 " + DateTime.Now);
                Thread.Sleep();
            });
            await Task.Run(() =>       //Await会对线程进行优化。
            {
                Console.WriteLine(Thread.CurrentThread.GetHashCode() + " Run2 " + DateTime.Now);
                Thread.Sleep();
            });
            Console.WriteLine(Thread.CurrentThread.GetHashCode() + " AwaitTest结束 " + DateTime.Now);
            return;
        }

        public static async void Excute3()
        {
            Console.WriteLine(Thread.CurrentThread.GetHashCode() + " 开始 Excute3 " + DateTime.Now);
            await SingleNoAwait();
            Console.WriteLine(Thread.CurrentThread.GetHashCode() + " 结束 Excute3 " + DateTime.Now);
        }
        public static async Task SingleNoAwait()
        {
            Console.WriteLine(Thread.CurrentThread.GetHashCode() + " SingleNoAwait开始 " + DateTime.Now);
            Task.Run(() =>
            {
                Console.WriteLine(Thread.CurrentThread.GetHashCode() + " Run1 " + DateTime.Now);
                Thread.Sleep();
            }).GetAwaiter().GetResult(); //用来获取线程返回值的。这个逻辑是这样的，如果想要获取线程返回结果，就自然要等待线程结束。
            Task.Run(() =>
            {
                Console.WriteLine(Thread.CurrentThread.GetHashCode() + " Run2 " + DateTime.Now);
                Thread.Sleep();
            }).GetAwaiter().GetResult();
            Console.WriteLine(Thread.CurrentThread.GetHashCode() + " SingleNoAwait结束 " + DateTime.Now);
            return;
        }

    }
}