其实这两个关键字的功效比之前的异步方法调用有一个好处,那就是异步阻塞的方法可以有返回值。之前都是通过回调函数实现,执行上下文会切换,不过和这个执行过程类似。可以对这两个关键字这么理解:遇到async的语句是异步的,遇到await的语句是阻塞的。
using System; using System.Collections.Generic; using System.Diagnostics; using System.Linq; using System.Text; using System.Threading; using System.Threading.Tasks; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { Debug.WriteLine("{0} Main Start.", DateTime.Now); Thread1(); Debug.WriteLine("{0} Main End.", DateTime.Now); Console.In.ReadLine(); } private static async void Thread1() { var result = await Proc1(); //此处会阻塞 Debug.WriteLine("{0} result={1}.", DateTime.Now, result); } private static Task<int> Proc1() //注意此处返回类型的定义 { return Task.Run(() => { Debug.WriteLine("{0} Proc 1 start.", DateTime.Now); Thread.Sleep(5000); Debug.WriteLine("{0} Proc 1 end.", DateTime.Now); return 10; }); } } }
程序输出:
10/18/2016 11:37:10 Main Start. 10/18/2016 11:37:10 Main End. 10/18/2016 11:37:10 Proc 1 start. 10/18/2016 11:37:15 Proc 1 end. 10/18/2016 11:37:15 result=10.
private async void MyWebClient_Navigating(string url) { await Task.Run(() => { }); //语法有点扯淡,有了这句编译就能通过 DetailNavigate(url); //同步方法 }