CodeGo.net>如何模拟一个昂贵的异步操作？

this page中的代码真的是模拟长时间运行任务的最佳方法吗？

我研究过的控制台应用程序非常简单,并且看起来还不错.

我不确定是否可以将DoExpensiveCalculation换成Async方法,例如来自HttpClient的GetStringAsync而不出现问题.

using System;
using System.Threading.Tasks;

namespace ExpensiveAsync
{
    public class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("started");

            var t = CalculateResult("stuff and that");

            Console.WriteLine("press return");
            Console.ReadLine();
        }

        public static async Task<string> CalculateResult(string data)
        {
            // This queues up the work on the threadpool.
            var expensiveResultTask = Task.Run(() => DoExpensiveCalculation(data));

            // Note that at this point, you can do some other work concurrently,
            // as CalculateResult() is still executing!

            Console.WriteLine("concurrent");

            // Execution of CalculateResult is yielded here!
            var result = await expensiveResultTask; // CalculateResult returns the Task object here

            Console.WriteLine("synchronous"); // this code runs once the DoExpensiveCalculation method has finished

            return result;
        }

        public static string DoExpensiveCalculation(string data)
        {
            var completionTime = DateTime.Now.AddSeconds(3);

            Console.WriteLine("begin");

            while (DateTime.Now < completionTime) ;

            Console.WriteLine("finish");

            return data;
        }
    }
}

解决方法:

该代码的结构意味着DoExpensiveCalculation是CPU绑定的操作.如果要在不占用CPU的情况下进行CPU绑定的操作,则Thread.Sleep是合适的选项.

I’m not sure if I could swap out DoExpensiveCalculation for an an Async method, like GetStringAsync from HttpClient without issue.

好吧,那是完全不同的. GetStringAsync不是CPU绑定的操作；这是一个受I / O约束的操作.

I / O绑定操作自然是异步的,可以直接与async和await一起使用.与CPU绑定的操作自然是同步的,因此有时您需要使用Task.Run.在这种情况下,“有时”通常表示“当您在UI线程上时”,以便在执行CPU绑定操作时不会冻结UI.当将CPU绑定的操作包装在Task.Run中时,可以将其视为异步,即从UI线程等待它.

您的示例代码是一个控制台应用程序,通常不需要使用Task.Run.控制台应用程序通常运行它们需要运行和退出的任何代码；在大多数情况下,不需要保持响应状态的UI,因此不需要Task.Run.

标签：net-core,async-await,console-application,c
来源： https://codeday.me/bug/20191108/2006892.html