Making a progress bar update in real time in wpf

Question

I'm having some trouble making the progress bar show the updates in real time.

This is my code right now

for (int i = 0; i < 100; i++)
{
     progressbar1.Value = i;
     Thread.Sleep(100);
}

But for some reason the progress bar shows empty when the function runs, and then nothing until the function finishes running. Can someone explain to me how this can be done? I'm new to C#/WPF so I'm not 100% sure on how I would implement a Dispatcher on a different thread (as seen on some other posts) to fix this problem.

To clarify, my program has a button which when press, grabs the value from a textbox, and uses an API to retrieve info, and create labels based on it. I want the progress bar to update after every row of data is finished processing.

This is what I have right now:

private async void search(object sender, RoutedEventArgs e)
{
    var progress = new Progress<int>(value => progressbar1.Value = value);
    await Task.Run(() =>
    {
        this.Dispatcher.Invoke((Action)(() =>
        {
             some pre-processing before the actual for loop occur
             for (int i = 0; i < numberofRows; i++)
             {
                  label creation + adding
                  ((IProgress<int>)progress).Report(i);
             }
        }));
    });
}

Thank you!

Answer 1

You should use BackgroundWorker included in .NET, which provides you with methods for reporting the progress of a background thread in an event. The thread which created the BackGroundWorker automatically calls this event.

The BackgroundWorker.ProgressChanged can be used to report the progress of an asynchronous operation to the user.

// This event handler updates the progress bar. 
private void backgroundWorker1_ProgressChanged(object sender,
    ProgressChangedEventArgs e)
{
    this.progressBar1.Value = e.ProgressPercentage;
}

Refer to MSDN for more information about using this.

Answer 2

If you are using .NET 4.5 or later, you can use async/await:

var progress = new Progress<int>(value => progressBar.Value = value);
await Task.Run(() =>
{
    for (int i = 0; i < 100; i++)
    {
        ((IProgress<int>)progress).Report(i);
        Thread.Sleep(100);
    }
});

You need to mark your method with async keyword to be able to use await, for example:

private async void Button_Click(object sender, RoutedEventArgs e)

Answer 3

Managed to make it work. All I needed to do is instead of making it just

progressBar1.value = i;

I just had to do

progressbar1.Dispatcher.Invoke(() => progressbar1.Value = i, DispatcherPriority.Background);