How to update text and progress bar in WPF without blocking the Thread?

Question

I have my window with a progress bar in it.

So in my "Do" Method, I want to change a status text and my progress bar without blocking the UI:

public void Do()
{
   ProgressBar.Value = 0;
   StateLabel.Content = "Start..."

   // Do Things   

   ProgressBar.Value = 50;
   StateLabel.Content = "Running part 2"

   // Do things

   ProgressBar.Value = 100;
   StateLabel.Content = "Finished. Closing progress window..."

   Thread.Sleep(1000);
   this.Close();
}

Can you try this? Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background, new Action(delegate () { //update UI Code here })); — mohammed mazin, May 07 '21 at 11:14
Change the declaration to `public async Task Do()` and move the "things" into a Task Action: `await Task.Run(() => { // Do things });`. Do not forget to await the method when you call it: `await Do();`. — Clemens, May 07 '21 at 11:30
Do not call Thread.Sleep in the UI thread. Use `await Task.Delay(1000);` instead. — Clemens, May 07 '21 at 11:33

score 1 · Accepted Answer · answered May 07 '21 at 12:35

Just in addition to the comments here should be a working snippet for your challenge:

    private void MainWindowButton_OnClick(object sender, RoutedEventArgs e)
    {
        ((MainWindowViewModel)this.DataContext).ButtonClickEvent();
        Application.Current.Dispatcher.Invoke(Do);
    }

    public async Task Do()
    {


        myLabel.Content = "Start...";

        // Do Things   
        await Task.Delay(1000);
        myLabel.Content = "Running part 2";

        // Do things
        await Task.Delay(1000);
        myLabel.Content = "Finished.";
    }

To learn more about to go around freezes in WPF I found this question quite instructive.

score 1 · Answer 2 · answered May 07 '21 at 13:37

The key point here is that you cannot both "do things" that blocks and update a ProgressBar on the same thread simultaneously.

You should display the progress bar on the UI thread, start a task that performs the long-running work on a background thread and then hide the progress bar once that task has finished:

public async Task Do()
{
    ProgressBar.Value = 0;
    StateLabel.Content = "Start...";

    await Task.Run(() =>
    {
        // Do things ...
        Thread.Sleep(1000);
    });

    ProgressBar.Value = 50;
    StateLabel.Content = "Running part 2";

    await Task.Run(() =>
    {
        // Do things ...
        Thread.Sleep(1000);
    });

    ProgressBar.Value = 100;
    StateLabel.Content = "Finished. Closing progress window...";

    this.Close();
}

How to update text and progress bar in WPF without blocking the Thread?

2 Answers2