Why does the BackgroundWorker in WPF need Thread.Sleep to update UI controls?
- by user364060
namespace WpfApplication1
{
/// <summary>
/// Interaction logic for Window1.xaml
/// </summary>
public partial class Window1 : Window
{
BackgroundWorker bgWorker;
Action<int> myProgressReporter;
public Window1()
{
InitializeComponent();
bgWorker = new BackgroundWorker();
bgWorker.DoWork += bgWorker_Task;
bgWorker.RunWorkerCompleted += myWorker_RunWorkerCompleted;
// hook event to method
bgWorker.ProgressChanged += bgWorker_ReportProgress;
// hook the delegate to the method
myProgressReporter = updateProgress;
bgWorker.WorkerReportsProgress = true;
}
private void myWorker_RunWorkerCompleted(object sender, System.ComponentModel.RunWorkerCompletedEventArgs e)
{
object result;
result = e.Result;
MessageBox.Show(result.ToString());
progressBar1.Value = 0;
button1.IsEnabled = true;
}
private void bgWorker_ReportProgress(object sender, ProgressChangedEventArgs e)
{
System.Windows.Threading.Dispatcher disp = button1.Dispatcher;
disp.BeginInvoke(myProgressReporter,e.ProgressPercentage);
//Dispatcher.BeginInvoke(myProgressReporter, DispatcherPriority.Normal, e.ProgressPercentage);
}
private void updateProgress(int progressPercentage)
{
progressBar1.Value = progressPercentage;
}
private void bgWorker_Task(Object sender, DoWorkEventArgs e)
{
int total = 1000;
for (int i = 1; i <= total; i++)
{
if (bgWorker.WorkerReportsProgress)
{
int p = (int)(((float)i / (float)total) * 100);
bgWorker.ReportProgress(p);
}
Thread.Sleep(1); // Without Thread.Sleep(x) the main thread freezes or gives stackoverflow exception,
}
e.Result = "Completed";
}
private void button1_Click(object sender, RoutedEventArgs e)
{
if(!bgWorker.IsBusy)
bgWorker.RunWorkerAsync("This is a background process");
button1.IsEnabled = false;
}
}
}
