wpf progressbar doesn't update on last ProgressChanged - wpf

Question

I making some UI and I have ProgressBar in it. Using MVVM pattern.
XAML:
<ProgressBar Grid.Row="2" Minimum="0" Maximum="100" Value="{Binding CurrentProgress, Mode=OneWay}"/>
ViewModel (simplified):
class MyClass : ViewModelBase
{
/// <summary>
/// Fields
/// </summary>
private int _currentProgress;
private readonly BackgroundWorker _worker;
private int _step;
/// <summary>
/// Properties
/// </summary>
public int CurrentProgress
{
get
{
return _currentProgress;
}
set
{
if (_currentProgress != value)
{
_currentProgress = value;
RaisePropertyChanged("CurrentProgress");
}
}
}
/// <summary>
/// Constructor
/// </summary>
public MyClass()
{
_step = 10;
_currentProgress = 0;
_worker = new BackgroundWorker();
_worker.DoWork += DoWork;
_worker.WorkerReportsProgress = true;
_worker.ProgressChanged += ProgressChanged;
_worker.RunWorkerCompleted += RunWorkerCompleted;
}
/// <summary>
/// Command
/// </summary>
private RelayCommand _myCommand;
public RelayCommand MyCommand
{
get
{
return _myCommand ?? (_myCommand =
new RelayCommand(_worker.RunWorkerAsync, CanMyCommand));
}
}
private bool CanMyCommand()
{
return true;
}
/// <summary>
/// Handlers
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void DoWork(object sender, DoWorkEventArgs e)
{
for (int i = 0; i < 10; i++)
ConsumingMethod();
}
private void RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
Thread.Sleep(5000);
Messenger.Default.Send(new CloseAddDocumentWindow(String.Empty));
}
private void ProgressChanged(object sender, ProgressChangedEventArgs e)
{
CurrentProgress = e.ProgressPercentage;
}
/// <summary>
/// Method
/// </summary>
private void ConsumingMethod()
{
CurrentProgress += _step;
}
}
Code-Behind:
Messenger.Default.Register<CloseAddDocumentWindow>(this, nm =>
{
if (nm.Sender == DataContext)
Close();
});
So, this
Messenger.Default.Send(new CloseAddDocumentWindow(String.Empty));
is the problem. That line close window as u see. If I comment that line, progressbar works good. 10, 20, 30, ... 100% I see. But else, progressbar looks like 10, 20, 30, ... 90%, some waiting and window closing! I try to use Thread.Sleep(5000), to give the progressbar some time to drawing. But even that doesn't help. So, how can I see last persentage change if window closing immediately after that?

Answer 1

For any future reader:
BackgroundWorker's DoWork is performed on a new thread, allowing work to occur without locking the UI for instance. The RunWorkerCompleted functionality will be ran on the calling thread for you, this means it is back on the UI thread and any work done here can lock the UI.
ProgressBar is being updated via different thread, allowing it to update. But as soon as the value goes from 90 to 100, the UI is performing this Close. When OP added the Sleep(5000); it was in the Completed which is the UI thread thus preventing the ProgressBar from showing a full 100%.
Resolution is to move the sleep from Completed into the DoWork loop, or at least after the loop, to see the ProgressBar hit 100%, before sending the close.