C# async await 学习笔记1

由于我的开发工具为vs.net 2010（.net 4.0)，需先做以下两步才能进行：

1.下载并安装Async CTP (http://www.microsoft.com/en-us/download/details.aspx?id=9983)

2.添加AsyncCtpLibrary.dll的引用，我用的是win7在（C:\Users\Administrator\Documents\Microsoft Visual Studio Async CTP\Samples）

 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Threading;



namespace ConsoleApplication1

{

    class Program

    {

        static Task<string> LongTimeTask()

        {          

            Console.WriteLine("LongTimeTask开始:" + DateTime.Now.ToString() + "  ThreadId:" + Thread.CurrentThread.ManagedThreadId);



            Task<string> task = new Task<string>(() => { Thread.Sleep(5000); return "这是任务返回值"; });

            task.Start();



            Console.WriteLine("LongTimeTask结束:" + DateTime.Now.ToString());



            return task;

        }



        static async void AsyncCall()

        {

            Console.WriteLine("AsyncCall开始：" + DateTime.Now.ToString() + "  ThreadId:" + Thread.CurrentThread.ManagedThreadId);



            string result = await LongTimeTask(); //await调用的方法需要返回Task或Task<T>，且调用await所在的方法要有async关键字

            Console.WriteLine("AsyncCall:" + result);



            Console.WriteLine("AsyncCall结束:" + DateTime.Now.ToString());

        }   



        static void Main(string[] args)

        {

            Console.WriteLine("Main开始：" + DateTime.Now.ToString() + "  ThreadId:" +Thread.CurrentThread.ManagedThreadId);

            AsyncCall();   

            Console.WriteLine("Main结束:" + DateTime.Now.ToString());      

            Console.ReadLine();

        }

    }

}

 

运行结果：

 不知大家注意到，里面的ThreadId是一致的。

 

 需要注意的是，并不是加了async，就是异步了（而是得里面有调用await方法），例如，下面其实是同步执行的

 static async void SyncCall()

        {

            Thread.Sleep(5000);

        }



        static void Main(string[] args)

        {

            Console.WriteLine("Main开始：" + DateTime.Now.ToString());

            // AsyncCall();

            SyncCall();

            Console.WriteLine("Main结束:" + DateTime.Now.ToString());



            Console.ReadLine();

        }