C# 进度条在下载时不更新答案

【问题标题】：C# Progress bar doesn't update while downloadingC# 进度条在下载时不更新
【发布时间】：2018-05-21 16:48:05
【问题描述】：

我正在使用 BackgroundWorker 从 ftp 服务器下载文件，但只有在文件下载完成后进度才会更新。

进度条保持在 0，在下载期间冻结，并设置为 100。

这是我的代码：

    private void backgroundWorker1_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e) {
        FtpWebRequest request = (FtpWebRequest)WebRequest.Create(activeDownload.ftpPath);
        request.Credentials = new NetworkCredential(ftpUser, ftpPass);
        request.Method = WebRequestMethods.Ftp.DownloadFile;

        FtpWebResponse response = (FtpWebResponse)request.GetResponse();
        Stream responseStream = response.GetResponseStream();

        using (FileStream writer = new FileStream(activeDownload.localPath, FileMode.Create)) {

            long length = response.ContentLength;
            int bufferSize = 2048;
            int readCount;
            byte[] buffer = new byte[2048];
            long bytesread = 0;
            backgroundWorker1.ReportProgress(0);

            readCount = responseStream.Read(buffer, 0, bufferSize);
            while (readCount > 0) {
                bytesread += readCount;
                writer.Write(buffer, 0, readCount);
                backgroundWorker1.ReportProgress((int)(bytesread / activeDownload.fileSize) * 100);
                readCount = responseStream.Read(buffer, 0, bufferSize);
            }
        }

        response.Close();
        responseStream.Close();
    }

    private void backgroundWorker1_ProgressChanged(object sender, System.ComponentModel.ProgressChangedEventArgs e) {
        progressBar1.Value = e.ProgressPercentage;
    }

我做错了什么？任何帮助将不胜感激。

【问题讨论】：

你能说一下这是一个什么样的项目，好吗？某些项目（例如 VSTO）与 BGW 的行为不符，需要额外的功能才能使其正常工作
那么您是否调试过您提供给ReportProgress 的信息或进度条渲染问题？添加一些Debug.WriteLine。 + 我们需要minimal reproducible example。
我已经找到了解决方案。更多详情如下。

标签： c# .net download ftp progress-bar

【解决方案1】：

设置值，然后在下面运行

progressbar1.PerformStep()

你也可以这样做

progressBar1.Refresh()

【讨论】：

【解决方案2】：

看看以下链接是否有帮助：

From Stack 和 MSDN

以下是我在其中一个项目中实现的示例代码：

public ProcessFilesClass()
    {
        InitializeComponent();
        backgroundWorker1= new BackgroundWorker();
        backgroundWorker1.DoWork += new DoWorkEventHandler(backgroundWorker1_DoWork);
        backgroundWorker1.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backgroundWorker1_RunWorkerCompleted);
        backgroundWorker1.ProgressChanged += new ProgressChangedEventHandler(backgroundWorker1_ProgressChanged);
    }

private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        BackgroundWorker worker = sender as BackgroundWorker;
        var backgroundWorker = sender as BackgroundWorker;
        worker.WorkerReportsProgress = true;
        WorkerProcessMethod();
    }

private void WorkerProcessMethod()
    {
            //Process items in list box
            int itemsToProcess = someListBox.Items.Count;
            for (int i = 0; i < itemsToProcess; i++)
                {
                    int findPercentage = ((i + 1) * 100) / someListBox.Items.Count;
                     if (backgroundWorker1 != null) { backgroundWorker1.ReportProgress(findPercentage, null); }
                }
    }

private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
           progressBar1.Value = e.ProgressPercentage;

    }

private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
          //DisableProgressBarStatus
           this.Close();            
    }

【讨论】：

【解决方案3】：

好吧，事实证明我做的一切都很好，但是我解析了错误的百分比。除以两个 long（bytesread 和 activeDownload.fileSize）返回 0。因此，进度卡在 0%。

下面是正确的解析：

backgroundWorker1.ReportProgress(Convert.ToInt32((((double)bytesread / activeDownload.fileSize) * 100)));

【讨论】：