using System;

using System.Threading;

using System.Threading.Tasks;



namespace ConsoleApp1

{

    class Program

    {

        static void Main(string[] args)

        {

            Console.WriteLine($"开始, thread id = {Thread.CurrentThread.ManagedThreadId}");

            test();

            Console.WriteLine($"主线程test完毕, thread id = {Thread.CurrentThread.ManagedThreadId}");

            Console.WriteLine("按任意键结束........");

            Console.ReadKey();

        }



        private static async void test()

        {

            Console.WriteLine($"test, thread id = {Thread.CurrentThread.ManagedThreadId}");

            var task = Task.Run(async () =>

            {

                int cnt = 0;

                while (cnt++ < 20)

                {

                    await Task.Delay(1000);

                    Console.WriteLine($"while, thread id = {Thread.CurrentThread.ManagedThreadId}");

                }

            });

            await Task.WhenAll(task);   //await语句并未阻塞4的执行

            Console.WriteLine($"while 完成, thread id = {Thread.CurrentThread.ManagedThreadId}");

        }

    }

}

开始, thread id = 1

test, thread id = 1

主线程test完毕, thread id = 1

按任意键结束........

while, thread id = 4

while, thread id = 4

while, thread id = 4

while, thread id = 7

while, thread id = 4

while, thread id = 4

while, thread id = 4

while, thread id = 4

while, thread id = 4

while, thread id = 6

while, thread id = 6

while, thread id = 4

while, thread id = 4

while, thread id = 6

while, thread id = 6

while, thread id = 6

while, thread id = 7

while, thread id = 7

while, thread id = 7

while, thread id = 4

while 完成, thread id = 4

  private async void button1_Click(object sender, EventArgs e)

        {

            await semaphore.WaitAsync();

            await WaitButton2Click();

            await semaphore.WaitAsync();

            MessageBox.Show("我等到了button2的点击");

            semaphore.Release();



        }

        System.Threading.SemaphoreSlim semaphore = new SemaphoreSlim(1);

        async Task WaitButton2Click()

        {

            EventHandler action = null;

            action = (object sender1, EventArgs e1) =>

           {

               semaphore.Release();

               button2.Click -= action;

           };

            button2.Click += action;



        }

private async void button1_Click(object sender, EventArgs e)

        {

           //当前还是同步执行，并没有开始异步 所以线程为UI线程(主线程:线程1)

            Console.WriteLine($"当前主线程的ID是{Thread.CurrentThread.ManagedThreadId}");

            for (int i = 0; i < 100; i++)

            {

               //第一次循环(i=0)时，没有开始任何异步等待(await)所以依然是主线程

                Console.WriteLine($"当前{i}的ID是{Thread.CurrentThread.ManagedThreadId}");



                //第一次循环(i=0)UI线程会阻塞100ms(程序窗口会失去响应100ms)，你可以时间改长一点观察以下。

                Thread.Sleep(100);

              

              //此处才开始异步，await机制可以参考两位大神说的，大致就是.net从线程池选择合适的线程执行

              //第二次循环(i=1)时，.net重新执行await。      

              //也就是说从第一次循环的await开始至此方法(button1_Click)结束都是异步 。每次执行至await .net会重新从线程池中选择合适线程。     

               await Task.Run(() => 

                 {

                     textBox1Set(i);

                 });

            }



            Console.WriteLine($"结束了");

        }

 

        public void textBox1Set(int I)//供当前及后续类写日志用

        {

            Console.WriteLine($"当前{I}的textBox1SetID是{Thread.CurrentThread.ManagedThreadId}");



            // textBox1.Invoke意思就是将代码委托至textBox1创建的线程执行，所以一定是UI线程

            //如果使用的时.net framework Winfrom控件的Invoke(Control.Invoke)与委托的Invoke(delegate.Invoke)机制是不同的，

            //相关资料有很多，自己搜。



            textBox1.Invoke((EventHandler)delegate

            {

                textBox1.Text = I.ToString();

                Console.WriteLine($"当前{I}的textBox1SetID的BeginInvoke是{Thread.CurrentThread.ManagedThreadId}");

            });

        }