C# 线程死锁案例

 

 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));
            }

            //这一步会造成deadlock,应为
            var results = Task.WhenAll(downloadWebsiteTasks).Result;//Result指示阻塞当前线程(UI)，等待结果返回
            foreach (var result in results)
            {
                //界面打印结果
                Textbox.Text += result;
            }
        }


        private async Task<string> DownloadWebSiteAsync(string url)
        {
            //ConfigureAwait指示线程返回后，回到当前线程（UI）
            var response = await httpClient.GetAsync(url).ConfigureAwait(false);//改成false,继续使用线程池里的线程运用下面的代码，避免死锁
            var responsePayloadBytes = await response.Content.ReadAsByteArrayAsync().ConfigureAwait(false);//改成false,继续使用线程池里的线程运用下面的代码，避免死锁

            //回到UI线程返回字符串
            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)
        {

        }
    }