Question

我有以下代码从网站获取数据

    private void BeginCreationButton_Click(object sender, RoutedEventArgs e)
    {
        //Log("INFO", "Beggining ad creation");
        GeneralProgressBar.Visibility = Visibility.Visible;

        foreach(var ad in ads)
        {
            string adUh = string.Empty;
            string errorMsg = string.Empty;
            bool error = false;

            //Task<string> uhFetch = Task<string>.Factory.StartNew(() => GetUhForAdvert());
            Task task = Task.Factory.StartNew(() =>
            {
                HttpWebRequest newPromoRequest = WebRequest.Create("https://www.randomsite.com") as HttpWebRequest;
                newPromoRequest.CookieContainer = Cookies;
                newPromoRequest.Method = "GET";
                newPromoRequest.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8";
                string uh = string.Empty;

                HttpWebResponse response = (HttpWebResponse)newPromoRequest.GetResponse();

                if (response.StatusCode == HttpStatusCode.OK)
                {
                    using (Stream s = response.GetResponseStream())
                    {
                        using (StreamReader sr = new StreamReader(s, Encoding.GetEncoding(response.CharacterSet)))
                        {
                            HtmlDocument doc = new HtmlDocument();

                            doc.Load(sr);

                            adUh = doc.DocumentNode.SelectNodes("//form")[0].SelectNodes("//input")[0].Attributes[2].Value;
                        }
                    }
                }
            });

            try
            {
                task.Wait();
            }
            catch (AggregateException ae)
            {
                ae.Handle((x) =>
                {
                    errorMsg = x.Message + " | " + x.StackTrace;
                    error = true;

                    return error;
                });
            }

            if (error)
            {
                Log("ERROR", errorMsg);
            }

            Log("INFO", adUh);
        }
    }

然而，当任务正在执行时，UI被阻止但我不确定它为什么会发生。不确定它是流阅读还是HTML处理部分，因为我在没有这两个组件的项目的其他部分使用请求代码，它就像一个魅力。

Answer 1

请勿使用task.Wait();阻止您的UI线程。像这样按下按钮点击处理程序异步：

private async void BeginCreationButton_Click(object sender, RoutedEventArgs e)
{
    // code here...
}

......以及你打电话的地方：

task.Wait();

......这样称呼：

await task;

此外，您不需要使用Task.Factory.StartNew，只需使用(HttpWebResponse)await newPromoRequest.GetResponseAsync();并将任务的所有代码包含在try catch块中即可简化。

编辑：您可以阅读Stephen Cleary's blog了解有关此主题的详细说明。

UI被Task阻止

1 个答案: