How to change progressbar value when async task ru

问题:

i am using async await task to run this code and i want to change the progress bar when extracting

public async Task<string> DownloadAndExtractFile(string source, string destination, string ItemDownload) //source = File Location //destination = Restore Location
    {
        string zPath = @"C:\Program Files\7-Zip\7zG.exe";
        ProcessStartInfo pro = new ProcessStartInfo();
        pro.WindowStyle = ProcessWindowStyle.Hidden;
        pro.FileName = zPath;
        pro.Arguments = "x \"" + source + "\" -o" + destination;

        await Task.Run(() =>
        {
            Restore.frmRestore.progressBar1.Value = 50; //already set to public
            try
            {
                Process x = Process.Start(pro);
                Task.WaitAll();
                Restore.frmRestore.progressBar1.Value = 100;//already set to public
                x.Close();
                Console.WriteLine("Extract Successful.");
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }

        }
           );

        return "Success";
    }

how to change the progressbar value when task running. this is the error "Cross-thread operation not valid: Control 'progressBar1' accessed from a thread other than the thread it was created on."

回答1:

Use the Progress<T> type to report progress, as I describe on my blog:

public async Task<string> DownloadAndExtractFile(string source, string destination, string ItemDownload)
{
  string zPath = @"C:\Program Files\7-Zip\7zG.exe";
  ProcessStartInfo pro = new ProcessStartInfo();
  pro.WindowStyle = ProcessWindowStyle.Hidden;
  pro.FileName = zPath;
  pro.Arguments = "x \"" + source + "\" -o" + destination;

  IProgress<int> progress = new Progress<int>(
      value => { Restore.frmRestore.progressBar1.Value = value; });

  await Task.Run(() =>
  {
    progress.Report(50);
    try
    {
      Process x = Process.Start(pro);
      Task.WaitAll();
      progress.Report(100);
      x.Close();
      Console.WriteLine("Extract Successful.");
    }
    catch (Exception ex)
    {
      Console.WriteLine(ex.ToString());
    }
  });
  return "Success";
}

回答2:

You can use a Progress<T>. That allows you to inform the UI thread of your progress and update your progress bar.

So, at the place where call that task, do this:

Progress<int> progress = new Progress<int>(i => Restore.frmRestore.progressBar1.Value = i);
await DownloadAndExtractFile(source, destination, ItemDownload, progress);

And in your method you can use this progress like this:

public async Task<string> DownloadAndExtractFile(string source, string destination, string ItemDownload, IProgress<int> progress)
{
    // shortened for clarity
    await Task.Run(() =>
    {
        progress.Report(50);
        try
        {
            Process x = Process.Start(pro);
            Task.WaitAll();
            progress.Report(100);
            x.Close();
            Console.WriteLine("Extract Successful.");
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.ToString());
        }
    });

    return "Success";
}

Note: that you have to pass progress as interface type IProgress<int> to be able to access the Report method of that interface.

回答3:

Direct solution, but not as fancy as Progress<T>:

Create a function:

private void UpdateProgress(int percent)
{
  if (Restore.frmRestore.progressBar1.InvokeRequired)
  {
    UpdateProgress.Invoke(percent);
  }
  else
  {
    Restore.frmRestore.progressBar1.Value = percent;
  }
}

And then call it instead of setting the value directly.

To clarify: .Invoke does execute the function on the main thread (which is the UI-Thread.).

This does 1:1 what you wan't but I would use Progress<T>