Question

It seems to be possible in this project…

After they use pd = new ProgressDialog();, the new window appears.

How did they do that?

Answer 1

Let’s define next instances first:

BackgroundWorker worker;
ProgressDialog pd;

then show a form through the ShowDialog() method in the click handler:

private void btnReportProgress_Click(object sender, RoutedEventArgs e)
{
    int maxRecords = 1000;
    pd = new ProgressDialog();
    // doing something more...
    pd.ShowDialog();
}

ProgressDialog.xaml.cs class could have additional properties:

public string ProgressText
public int ProgressValue