c# - update UI in Task using TaskScheduler.FromCurrentSynchronizationContext

Question

I want to add some text to list box using Task and I simply use a button and place in click event this code:

TaskScheduler uiScheduler = TaskScheduler.FromCurrentSynchronizationContext();
Task.Factory.StartNew(() =>
{
    for (int i = 0; i < 10; i++)
    {
        listBox1.Items.Add("Number cities in problem = " + i.ToString());
        System.Threading.Thread.Sleep(1000);
    }
}, CancellationToken.None, TaskCreationOptions.None, uiScheduler);

but it does not work and UI locked until the end of the for loop.

Where is the problem ?

thanks :)

Answer 1

You could do all work in the thread, but then when you need to update the UI use the dispatcher:

Task.Factory.StartNew(() =>
{
  for (int i = 0; i < 10; i++)
  {
     Application.Current.Dispatcher.BeginInvoke(DispatcherPriority.Normal, 
        new Action(() => {listBox1.Items.Add("Number cities in problem = " + i.ToString()); }));
     System.Threading.Thread.Sleep(1000);
  }
});