BackgroundWorker的进度栏不起作用

Question

The BackgroundWorker's progressbar is not updated while doing some tasks. What I would like to reach is progressbar moving while iterating through each file in DirectoryInfo. Suppose we have 20 files of ".sql" while first file completed it should be 5%, 10% and etc. Here is my code.

private void CSV_Click(object sender, RoutedEventArgs e)
        {         
            try
            {
                btnExtract.IsEnabled = false;
                workerextract.RunWorkerAsync();

        }
        catch (Exception ex)
        {
            System.Windows.MessageBox.Show(ex.Message);
        }
    }

    private void workerextract_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
    {
        try
        {
           this.Dispatcher.Invoke(() =>
            {

                DirectoryInfo di = new DirectoryInfo(txtQueryfolder.Text);
                files = di.GetFiles("*.sql").Count();
                currentfile = 0;

                foreach (FileInfo fi in di.GetFiles("*.sql"))
                {
                    // Open the text file using a stream reader.
                    using (StreamReader sr = new StreamReader(fi.FullName))
                    {
                        // Read the stream to a string, and write the string to the console.
                        string line = sr.ReadToEnd();

                        //System.Windows.MessageBox.Show(line);
                        ExtractToCSV(line, System.IO.Path.GetFileNameWithoutExtension(fi.Name));
                        currentfile++;
                    }
                    int percentage = (currentfile + 1) * 100 / files;
                    workerextract.ReportProgress(percentage);
                }

            });

        }
        catch(Exception ex)
        {
            System.Windows.MessageBox.Show(ex.Message);
        }
    }

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

    private void workerextract_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        btnExtract.IsEnabled = true;
        System.Windows.MessageBox.Show("CSV Data extraction finished!");
    }

I found that

private void workerextract_ProgressChanged(object sender, System.ComponentModel.ProgressChangedEventArgs e)

is called once at the end when 100%. Also,

private void workerextract_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)

never called as I do not see Message Box at the end.

So, I think I am doing something wrong here, could you please direct me on right way?

Answer 1

Using this.Dispatcher.Invoke in the BackgroundWorker 's DoWork event you are executing the whole operation in the UI thread; which is what BackgroundWorker born to avoid to do.

Also, you get an error unwrapping your code from the dispatcher because you are accessing an UI object, which is txtQueryfolder .

Just use:

private void workerextract_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
{
    string queryFolder = e.Argument.ToString();
    try
    {
        DirectoryInfo di = new DirectoryInfo(queryFolder);
        files = di.GetFiles("*.sql").Count();
        currentfile = 0;

        foreach (FileInfo fi in di.GetFiles("*.sql"))
        {
            // Open the text file using a stream reader.
            using (StreamReader sr = new StreamReader(fi.FullName))
            {
                // Read the stream to a string, and write the string to the console.
                string line = sr.ReadToEnd();

                //System.Windows.MessageBox.Show(line);

                // ExtractToCSV shouldn't access to a UI object.
                ExtractToCSV(line, System.IO.Path.GetFileNameWithoutExtension(fi.Name));
                currentfile++;
            }
            int percentage = (currentfile + 1) * 100 / files;
            workerextract.ReportProgress(percentage);
        }
    }
    catch (Exception ex)
    {
        // Don't use MessageBox in a thread different from the UI one. Just set the result (e.Result) and get that in the RunWorkerCompleted event.
        // System.Windows.MessageBox.Show(ex.Message);
    }
}

When you call the RunWorkerAsync method just add the parameter like below:

workerextrac.RunWorkerAsync(txtQueryfolder.Text);

Answer 2

The problem was in wrapping whole DoWork inside Dispatcher.Invoke. I need to wrap only those code where it is interacting with UI. So I changed the code appropriately and it works.

 private void workerextract_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
        {
            try
            {
                this.Dispatcher.Invoke(() =>
                {
                    di = new DirectoryInfo(txtQueryfolder.Text);
                });
                    files = di.GetFiles("*.sql").Count();
                    currentfile = 0;

                foreach (FileInfo fi in di.GetFiles("*.sql"))
                {
                    // Open the text file using a stream reader.
                    using (StreamReader sr = new StreamReader(fi.FullName))
                    {
                        // Read the stream to a string, and write the string to the console.
                        string line = sr.ReadToEnd();

                        this.Dispatcher.Invoke(() =>
                        {
                        //System.Windows.MessageBox.Show(line);
                        ExtractToCSV(line, System.IO.Path.GetFileNameWithoutExtension(fi.Name));
                        });

                        currentfile++;
                    }
                    int percentage = (currentfile + 1) * 100 / files;
                    workerextract.ReportProgress(percentage);
                }
        }
        catch(Exception ex)
        {
            System.Windows.MessageBox.Show(ex.Message);
        }
    }

Thanks to all for showing the direction.