using System;

using System.Collections.Generic;

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//using System.Linq;

//using System.Threading;

using System.Threading.Tasks;

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​

​

​

​

​

   public class Program

    {

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        //使用 Async 和 Await 的异步编程 https://docs.microsoft.com/zh-cn/dotnet/csharp/programming-guide/concepts/async/

        public static async Task Main()

        {

            var n = 20000;

            await SleepParallel(n);

            //await SleepSerial(n);

        }

​

        private static async Task<int> MiniTask(int i)

        {

            //Thread.Sleep(100);//共计用时:21.7秒

            //Task.Delay(100);//共计用时:0.12秒

            await Task.Delay(100);//SleepSerial共计用时:21.7秒,SleepParallel共计用时:0.12秒

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            Console.WriteLine(i);

            return await Task.FromResult(i);

        }

​

        public static async Task<int> SleepSerial(int n)

        {

            DateTime dtF = DateTime.Now;

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

            {

                await MiniTask(i);

            }

            //结束时间

            DateTime dtT = DateTime.Now;

            //计算总用时

            var dtSp = dtT - dtF;

            Console.WriteLine($"共计用时:{dtSp.TotalSeconds}秒");

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            return await Task.FromResult(n);

        }

​

        public static async Task<int> SleepParallel(int n)

        {

            DateTime dtF = DateTime.Now;

            var taskList = new List<Task<int>>();

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

            {

                var li = i;//局部变量，真实的任务编号

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                //边创建任务边执行，20000任务共计用时6.6秒

                //var task = Task.Run(async () => await MiniTask(li));

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                //创建所有任务后执行，20000任务共计用时4.4秒

                var task = MiniTask(i);

                taskList.Add(task);

​

                //Task.Run vs Task.Factory.StartNew https://devblogs.microsoft.com/pfxteam/task-run-vs-task-factory-startnew/

                //var t = Task.Factory.StartNew(async () => { await MiniTask(li); });

                //t.Wait();

            }

​

            //等待所有任务完成

            if (taskList.Count > 0)

            {

                // ReSharper disable once CoVariantArrayConversion

                Task.WaitAll(taskList.ToArray());

​

                ////所有任务执行结果

                //Console.WriteLine(string.Join(",", taskList.Select(t => t.Result).ToArray()));

            }

​

            //逐个处理返回结果

            //while (taskList.Count > 0)

            //{

            //    var finishedTask = await Task.WhenAny(taskList);

            //    //Console.WriteLine(finishedTask.Result);

            //    await finishedTask;

            //    taskList.Remove(finishedTask);

            //}

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            //结束时间

            DateTime dtT = DateTime.Now;

            //计算总用时

            var dtSp = dtT - dtF;

            Console.WriteLine($"共计用时:{dtSp.TotalSeconds}秒");

​

            return await Task.FromResult(n);

        }

    }

​