Question

I have a button and a label on my UI. When i clicks on the button i want to show “In Progress” on the label until the for loop finished and then again the same label should show the result of the collection.

private void button1_Click(object sender, RoutedEventArgs e)
{
  label1.Content = "In progress..";          
  List<string> intList = new List<string>();
  for (long i = 0; i <= 50000000; i++)
  {
    intList.Add("Test");
  }
  label1.Content = intList.ToString();
}

Answer 1

You’ll need to farm the work out to a background thread, otherwise your loop continues on the UI thread hence you see no “progress”.

You can use a BackgroundWorker or a Task to accomplish this:

private void button1_Click(object sender, RoutedEventArgs e)
{
    label1.Content = "In progress..";
    Task.Factory.StartNew<List<string>>(
    () =>
    {
        List<string> intList = new List<string>();
        for (long i = 0; i <= 50000000; i++)
        {
            intList.Add("Test");
        }

        return intList;
    })
    .ContinueWith(
        (t) => label1.Content = t.Result.ToString(),
        TaskScheduler.FromCurrentSynchronizationContext());
}