private async void Button_Click(object sender, RoutedEventArgs e){var client = new WebClient();var html = await client.DownloadStringTaskAsync(this.Url.Text);this.Output.Text = html;}//↓private void Button_Click(object sender, RoutedEventArgs e){Task.Factory.StartNew(() => {var client = new WebClient();var html = await client.DownloadString(this.Url.Text);this.Output.Text = html;});}