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C # - show download until it's finished?

In my C # application, I run the program by reading an HTML page and parsing some links from it and putting them in a richTextBox (for now). But the problem is that since it needs to read links, it takes some time, so when I run the program, it takes about 5 seconds to display the form. What I would like to do is show the form immediately and show the load cursor or disabled richTextBox. How should I do it? Here is an example of what is happening:

public Intro()
        {
            InitializeComponent();
            WebClient wc = new WebClient();
            string source = wc.DownloadString("http://example.com");

            HtmlAgilityPack.HtmlDocument doc = new HtmlAgilityPack.HtmlDocument();
            doc.LoadHtml(source);
            var nodes = doc.DocumentNode.SelectNodes("//a[starts-with(@class, 'url')]");
            foreach (HtmlNode node in nodes)
            {
                HtmlAttribute att = node.Attributes["href"];
                richTextBox1.Text = richTextBox1.Text + att.Value + "\n";

            }

        }
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2 answers

Ok, a bit (I hope everything is correct) an example of how you could do this using a parallel task library (which I like ...)

public Intro()
{
    InitializeComponent();

    richTextBox1.IsEnabled = false;
    Task.Factory.StartNew( () =>
    {
       WebClient wc = new WebClient();
       string source = wc.DownloadString("http://example.com");

       HtmlAgilityPack.HtmlDocument doc = new HtmlAgilityPack.HtmlDocument();
       doc.LoadHtml(source);
       var nodes = doc.DocumentNode.SelectNodes("//a[starts-with(@class, 'url')]");
       return nodes;
    }).ContinueWith( result =>
    {
      richTextBox1.IsEnabled = true;

      if (result.Exception != null) throw result.Exception;

      foreach (var node in result.Result)
      {
           HtmlAttribute att = node.Attributes["href"];
           richTextBox1.Text = richTextBox1.Text + att.Value + "\n";
      }

    }, TaskScheduler.FromCurrentSynchronizationContext());
}
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