(66) c# async await

1.使用 async await

2.返回值

        static void Main(string[] args)
        {
            Program p = new Program();
            Console.WriteLine(1);
            p.Go();
            Console.WriteLine(2);
            Console.ReadLine();
        }

        async Task Go()
        {
            Console.WriteLine(3);
            await a();
            Console.WriteLine(4);
        }
        async Task a()
        {
            Console.WriteLine(5);
            int i = await b();
            Console.WriteLine(i);
        }
        async Task<int> b()
        {
            Console.WriteLine(6);
            await Task.Delay(5000);
            Console.WriteLine(7);
            int i = 999;
            return i;
        }

 2以后暂停几秒后继续执行

3.异步lambda表达式

4.异步更新UI

 Random random = new Random();
        private void button1_Click(object sender, EventArgs e)
        {
            Test();
        }
        public async void Test()
        {
            while (1 == 1) 
            {
                string temp = await TestAsync();
                textBox1.Text = temp.ToString();
            }
        }

        Task<string> TestAsync()
        {
            return Task.Run(() => { 
                Thread.Sleep(1000);
                return random.Next(1, 100).ToString(); 
            });
        }

5.主线程异步 4.5新增

        static async Task Main(string[] args)
        {
            HttpClient httpClient = new HttpClient();
            var msg = await httpClient.GetAsync("https://www.baidu.com/");
            Console.WriteLine(msg.StatusCode);
            Console.ReadKey();
        }