await和async

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

namespace await和async
{
    class Program
    {
        static void Main(string[] args)
        {
            //AwaitAsync();
            //TaskRun();

            AwaitTaskRun();

        }

        #region await和async
        private static void AwaitAsync()
        {
            Say();                             //由于Main不能使用async标记
            Console.ReadLine();
        }

        private async static void Say()
        {
            var t = TestAsync();
            Thread.Sleep();                                     //主线程在执行一些任务
            Console.WriteLine("Main Thread");                       //主线程完成标记
            Console.WriteLine(await t);                             //await 主线程等待取异步返回结果
        }
        static async Task<string> TestAsync()
        {
            return await Task.Run(() =>
            {
                Thread.Sleep();                                 //异步执行一些任务
                return "Hello World";                               //异步执行完成标记
            });
        }
        #endregion

        #region task
        public static void TaskRun()
        {
            Console.WriteLine("执行GetReturnResult方法前的时间：" + DateTime.Now.ToString("yyyy-MM-dd hh:MM:ss"));
            var strRes = Task.Run<string>(() => { return GetReturnResult1(); });
            Console.WriteLine("执行GetReturnResult方法后的时间：" + DateTime.Now.ToString("yyyy-MM-dd hh:MM:ss"));
            Console.WriteLine("我是主线程，线程ID：" + Thread.CurrentThread.ManagedThreadId);
            Console.WriteLine(strRes.Result);
            Console.WriteLine("得到结果后的时间：" + DateTime.Now.ToString("yyyy-MM-dd hh:MM:ss"));

            Console.ReadLine();

        }

        static string GetReturnResult1()
        {
            Console.WriteLine("我是GetReturnResult里面的线程，线程ID：" + Thread.CurrentThread.ManagedThreadId);
            Thread.Sleep();
            return "我是返回值";
        }
        #endregion

        #region AwaitTaskRun
        /*
         * await:只能标记在async方法或Task对象前面；等待异步的执行结果。
         * async：标记异步方法，里面有异步执行则异步，没有则为普通方法，只能返回void、Task、Task<T>
         */

        public static void AwaitTaskRun()
        {
            Console.WriteLine("我是主线程，线程ID：{0}", Thread.CurrentThread.ManagedThreadId);
            TestAsync1();
            Console.ReadLine();
        }
        static async void TestAsync1()
        {
            Console.WriteLine("调用GetReturnResult()之前，线程ID：{0}。当前时间：{1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString("yyyy-MM-dd hh:MM:ss"));
            var name = GetReturnResult();
            Console.WriteLine("调用GetReturnResult()之后，线程ID：{0}。当前时间：{1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString("yyyy-MM-dd hh:MM:ss"));
            Console.WriteLine("得到GetReturnResult()方法的结果：{0}。当前时间：{1}", await name, DateTime.Now.ToString("yyyy-MM-dd hh:MM:ss"));

            Console.WriteLine("最后执行，线程ID：{0}。当前时间：{1}", Thread.CurrentThread.ManagedThreadId, DateTime.Now.ToString("yyyy-MM-dd hh:MM:ss"));
        }

        static async Task<string> GetReturnResult()
        {
            Console.WriteLine("执行Task.Run之前, 线程ID：{0}", Thread.CurrentThread.ManagedThreadId);
            return await Task.Run(() =>
            {
                Thread.Sleep();
                Console.WriteLine("GetReturnResult()方法里面线程ID: {0}", Thread.CurrentThread.ManagedThreadId);
                return "我是返回值";
            });
        } 

        #endregion
    }
}

需要等待结果执行，必须所有的方法用await，调用方法的时候也需要。