如何将C#旧版多任务代码改写为符合async/await规范的现代写法

改写后的完整代码 #

using System;
using System.Threading;
using System.Threading.Tasks;

namespace TasksAsyncAwait
{
    class Program
    {
        static async Task Main(string[] args)
        {
            using CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
            CancellationToken cancellationToken = cancellationTokenSource.Token;

            Task taskOne = RunTaskOneAsync(cancellationToken);
            Task taskTwo = RunTaskTwoAsync(cancellationToken);

            await Task.WhenAll(taskOne, taskTwo);
            Console.WriteLine("Program done.");
        }

        private static async Task RunTaskOneAsync(CancellationToken cancellationToken)
        {
            Console.WriteLine("Task 1 start");
            for (int i = 0; i < 10; i++)
            {
                cancellationToken.ThrowIfCancellationRequested();
                Console.WriteLine($"T1: {i}");
                await Task.Delay(500, cancellationToken);
            }
            Console.WriteLine("Task 1 complete");
        }

        private static async Task RunTaskTwoAsync(CancellationToken cancellationToken)
        {
            Console.WriteLine("Task 2 start");
            for (int i = 0; i < 5; i++)
            {
                cancellationToken.ThrowIfCancellationRequested();
                Console.WriteLine($"T2: {i}");
                await Task.Delay(300, cancellationToken);
            }
            Console.WriteLine("Task 2 complete");
        }
    }
}

主要改动说明 #

• 将原来Task.Factory.StartNew包裹的业务逻辑抽为独立的异步方法，方法名加Async后缀符合C#异步编码规范
• 用非阻塞的await Task.Delay()替换原同步阻塞的cancellationToken.WaitHandle.WaitOne()，等待时不会占用线程空转，大幅提升资源利用率
• 用非阻塞的await Task.WhenAll()替换原同步阻塞的Task.WaitAll()，避免主线程卡死
• 为CancellationTokenSource添加using关键字，用完自动释放非托管资源，避免内存泄漏
• 所有异步操作都传递取消令牌，取消逻辑、执行效果和原代码完全一致

内容的提问来源于stack exchange，提问作者Nimral