使用httprequest后台工作程序將UI凍結1或2秒

Question

我的代碼有什么問題？ 后台工作程序是否未正確設置，導致UI凍結？ 似乎延遲開始於調用BeginGetResponse時，然后從Web服務器返回結果后正常恢復。

    private void updateProgressbar()
    {
        bgWorker = new BackgroundWorker();
        bgWorker.DoWork += new DoWorkEventHandler(bgWorker_DoWork);
        bgWorker.RunWorkerAsync();
    }

    private void bgWorker_DoWork(object sender, DoWorkEventArgs e)
    {
        string path = "http://www.somestring.com/script.php?a=b");
        Uri uriString = new Uri(path);

        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(uriString);
        request.UserAgent = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0)";
        request.BeginGetResponse(new AsyncCallback(ReadCallback), request);
    }

    private void ReadCallback(IAsyncResult asynchronousResult)
    {
        HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
        HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asynchronousResult);

            using (StreamReader streamReader1 = new StreamReader(response.GetResponseStream()))
            {
                string resultString = streamReader1.ReadToEnd();
                Deployment.Current.Dispatcher.BeginInvoke(() =>
                    {
                        JsonMainProgressbar progressBarValue;
                        progressBarValue = JsonConvert.DeserializeObject<JsonMainProgressbar>(resultString);
                        this.ProgressBar.Value = Convert.ToInt32(progressBarValue.userclicks / progressBarValue.countryclicks * 100);
                        this.txtContribution.Text = "your contribution: " + this.ProgressBar.Value + "%";
                        Debug.WriteLine("Progressbar updated");
                    });
            }

     }

Answer 1

我認為您對UI線程做了太多工作，而在后台線程上ReadCallback卻做得不夠。 嘗試在傳遞給BeginInvoke()的lambda函數之外盡可能多地（*）移動。

（*），即安全無InvalidCrossThreadExceptions或競爭條件...

在這種情況下，請嘗試以下操作：

string resultString = streamReader1.ReadToEnd();
JsonMainProgressbar progressBarValue;
progressBarValue = JsonConvert.DeserializeObject<JsonMainProgressbar>(resultString);
int progressBarValueInt = Convert.ToInt32(progressBarValue.userclicks /
        progressBarValue.countryclicks * 100);

Deployment.Current.Dispatcher.BeginInvoke(() =>
{
    this.ProgressBar.Value = progressBarValueInt;
    this.txtContribution.Text = "your contribution: " + progressBarValueInt + "%";
    Debug.WriteLine("Progressbar updated");
 });

（假設您可以在后台線程中安全地使用JsonMainProgressBar ）