WPF Binding Render Gui Progress

I know that there are several implementations here and there, but i was still not able to 'lock' on something really useful...

Whenever i set some component DataContext or ItemsSource to some big object, there is this 'render time frozen GUI' which make the app real annoying (even when using Virtualization).

I know i can iterate the object and set the items one by one and show progress, but i am looking for some other approach which can let me show some moving indication while GUI is rendering. I also prefer to have some progress bar and not only make the mouse cursor change.

Is there a decent 开发者_StackOverflow中文版way to achieve the followings?

Many Thanks

Zamboni example is a very good one, but still does not solve the frozen GUI problem.

As mentioned, there is no currently simple way of having something 'alive' to update a gui control while GUI is busy rendering.

I currently found some event that is 'alive and kicking' while gui is rendering, althogh it should be turned off when not needed as it can fire something like 60 times per second.

CompositionTarget.Rendering += ReportRenderProgress;

You can then implement ReportRenderProgress() anyway you like to signal you progress bar to update. Currently, i dont see any better solution available in WPF to update a progress indication while rendering so i am marking this as the answer.

This is actually a problem. You are using the GUI thread to fill the data (from object structure into GUI). The GUI thread is required both to read Windows message queue (prevent app from freezing, allow app to be moved/respond) and it is required to do any updates to the GUI.

One solution could be to slowly fill the the object structure after binding. This would have to be done from the GUI thread, so you could add DoEvents() and/or some percent indicator+forced refresh to make application seem alive.

I am interested to hear if anyone has a better solution though.

BackgroundWorker has everything you need.

EDIT

In WPF the Dispatcher is being employed automatically to invoke cross-thread method calls. Check out Build More Responsive Apps With The Dispatcher in MSDN magazine.

I also put together some code fragments from a ViewModel that shows a BackgroundWorker updating a progress bar.

<ProgressBar 
    VerticalContentAlignment="Stretch" VerticalAlignment="Stretch"
    HorizontalAlignment="Stretch"
    Minimum="0" Maximum="100"
    Value="{Binding Path=BarPosition, Mode=TwoWay}"/>


// configure the background worker...
_backgroundWorker = new BackgroundWorker();
_backgroundWorker.WorkerReportsProgress = true;
_backgroundWorker.WorkerSupportsCancellation = true;
_backgroundWorker.DoWork += new DoWorkEventHandler(_backgroundWorker_DoWork);
_backgroundWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(_backgroundWorker_RunWorkerCompleted);
_backgroundWorker.ProgressChanged += new ProgressChangedEventHandler(_backgroundWorker_ProgressChanged);

// control progress bar position
private int _barPosition = 0;
public int BarPosition
{
   get { return _barPosition; }
   set
   {
      _barPosition = value;
      OnPropertyChanged("BarPosition");
   }
}

// long operation
void _backgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
  BackgroundWorker bw = sender as BackgroundWorker;
  if (bw != null)
  {
     int pos;

     for (int i = 0; i < 100; ++i
     {
        // report progress here for our long running operation..
        pos = i/100;
        bw.ReportProgress(pos);
        Thread.Sleep(1000);            // fake long operation
     }
  }
}

// report progress,,,
void _backgroundWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
   BackgroundWorker bw = sender as BackgroundWorker;
   if (bw != null)
   {
      BarPosition = e.ProgressPercentage;
   }
}

// reset scroll bar position
void _backgroundWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
   BackgroundWorker bw = sender as BackgroundWorker;
   if (bw != null)
   {
     BarPosition = 0;

     // Forcing the CommandManager to raise the RequerySuggested event to refresh UI...
     CommandManager.InvalidateRequerySuggested();
   }
}