BackgroundWorker OnProgressChanged is still running after running RunWorkerCompleted

Question

My application used BackgroundWorker to upload a file to an FTP server. Everything works fine, but it seems that the OnProgressChanged event OnProgressChanged not working as it should.

I, although OnProgressChanged will finish completely after the RunWorkerCompleted event, but it is not.

In my case, the OnProgressChanged event still fires, although RunWorkerComplete fired. Obviously, my progress indicator is still ongoing, as long as my file is already fully uploaded to the ftp server.

I tested in my debug mode and I see that after RunWorkerCompleted Fired, OnPorgressChanged still works.

My code is here.

  void FTP_DoWork(object sender, DoWorkEventArgs e) { BackgroundWorker bw = sender as BackgroundWorker; try { string filename = e.Argument.ToString(); if (filename != string.Empty) { FileInfo fileInf = new FileInfo(filename); FtpWebRequest reqFTP; if (!IsFolderExist(_defaultDir)) { MakeDefaultDir(_defaultDir); } reqFTP = GetRequest(this._host, this._port, GetDirName(_defaultDir) + "/" + fileInf.Name, this._user, this._pass); reqFTP.KeepAlive = false; reqFTP.Method = WebRequestMethods.Ftp.UploadFile; reqFTP.UseBinary = true; reqFTP.ContentLength = fileInf.Length; long FileSize = fileInf.Length; string FileSizeDescription = GetFileSize(FileSize); int ChunkSize = 4096, NumRetries = 0, MaxRetries = 50; long SentBytes = 0; byte[] Buffer = new byte[ChunkSize]; int BytesRead = 0; using (Stream requestStream = reqFTP.GetRequestStream()) { using (FileStream fs = File.Open(filename, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)) { BytesRead = fs.Read(Buffer, 0, ChunkSize); // read the first chunk in the buffer while (BytesRead > 0) { try { if (bw.CancellationPending) return; requestStream.Write(Buffer, 0, BytesRead); SentBytes += BytesRead; // Here is progress information string SummaryText = String.Format("Transferred {0} / {1}", GetFileSize(SentBytes), FileSizeDescription); bw.ReportProgress((int)(((decimal)SentBytes / (decimal)FileSize) * 100), SummaryText); } catch (Exception ex) { Console.WriteLine("Exception: " + ex.ToString()); if (NumRetries++ < MaxRetries) { fs.Position -= BytesRead; } else { throw new Exception(String.Format("Error occurred during upload, too many retries. \n{0}", ex.ToString())); } } BytesRead = fs.Read(Buffer, 0, ChunkSize); } } } } } catch (Exception ex) { if (OnFTPError != null) { OnFTPError(this, "Error was handled in Replaced File Uploading :" + ex.Message); } } } 

Any ideas on these issues? Thanks guys

Answer 1

This is most likely caused by an artifact introduced by the Vista update for the component of the main execution component, also present in Windows 7. To see it, start a new Winforms project and omit the progress bar and button on the form. Double-click the button and make the Click event handler as follows:

  private void button1_Click(object sender, EventArgs e) { if (progressBar1.Value == progressBar1.Maximum) progressBar1.Value = progressBar1.Minimum; else progressBar1.Value = progressBar1.Maximum; } 

Press F5 and press the button. Notice how the panel is animated, it moves smoothly from 0 to 100. It takes about a second.

Perhaps now you see the implication, this animation creates a lag. In other words, the visible value is always less than the programmed value, unless you give it enough time to catch up. You do not do this, you are constantly updating the value using the ProgressChanged event handler.

Unfortunately, they forgot to provide the ability to disable this animation. However, there is a trick; animation is disabled by default for decrements. What you can do is set the Value property twice, first value + 1, and then value. The bar instantly changes to the programmed value. The only drawback is that you cannot easily switch to 100%.