C# 多线程里的ConfigureAwait作用

 

 

 上述代码如下：

 public partial class Form1 : Form
    {
        private readonly HttpClient httpClient = new HttpClient();

        public Form1()
        {
            InitializeComponent();
        }

        private async Task DownloadWebsitesAsync()
        {
            List<Task<string>> downloadWebsiteTasks = new List<Task<string>>();

            foreach (var site in Contents.WebSites)
            {
                downloadWebsiteTasks.Add(DownloadWebSiteAsync(site));
            }

            //ConfigureAwait指示线程池里是否返回当前的线程（这里时UI线程），默认=true,
            //如果等于false指示不要返回当前线程，在线程池里利用线程继续执行后续的代码
            var results = await Task.WhenAll(downloadWebsiteTasks).ConfigureAwait(false);//注意ConfigureAwait=false

            foreach (var result in results)
            {
                //界面打印结果
                Textbox.Text += result;
            }
        }

        private async Task<string> DownloadWebSiteAsync(string url)
        {

            var response = await httpClient.GetAsync(url);
            var responsePayloadBytes = await response.Content.ReadAsByteArrayAsync();

            return $"Finish downloding data from {url}. Total bytes returned {responsePayloadBytes.Length}. {Environment.NewLine}";
        }


        private async void AsyncDownload_Click(object sender, EventArgs e)
        {
            Textbox.Text = "";

            var stopwatch = Stopwatch.StartNew();

            await DownloadWebsitesAsync();

            Textbox.Text += $"Elapsed time: {stopwatch.Elapsed}{Environment.NewLine}";
        }

        private void Result_TextChanged(object sender, EventArgs e)
        {

        }
    }

public class Contents
    {
        public static readonly IEnumerable<string> WebSites = new string[]
        {
            "https://www.zhihu.com",
            "https://www.baidu.com",
            "https://www.weibo.com",
            "https://www.stackoverflow.com",
            "https://docs.microsoft.com",
            "https://docs.microsoft.com/aspnet/core",
            "https://docs.microsoft.com/azure",
            "https://docs.microsoft.com/azure/devops",
            "https://docs.microsoft.com/dotnet",
            "https://docs.microsoft.com/dynamics365",
            "https://docs.microsoft.com/education",
            "https://docs.microsoft.com/enterprise-mobility-security",
            "https://docs.microsoft.com/gaming",
            "https://docs.microsoft.com/graph",
            "https://docs.microsoft.com/microsoft-365",
            "https://docs.microsoft.com/office",
            "https://docs.microsoft.com/powershell",
            "https://docs.microsoft.com/sql",
            "https://docs.microsoft.com/surface",
            "https://docs.microsoft.com/system-center",
            "https://docs.microsoft.com/visualstudio",
            "https://docs.microsoft.com/windows",
            "https://docs.microsoft.com/xamarin"
        };
    }