How to cancel Task await after a timeout period

Question

I am using this method to instantiate a web browser programmatically, navigate to a url and return a result when the document has completed.

How would I be able to s

Answer 1

I'm trying to take benefit from Noseratio's solution as well as following advices from Stephen Cleary.

Here is the code I updated to include in the code from Stephen the code from Noseratio regarding the AJAX tip.

First part: the Task NavigateAsync advised by Stephen

public static Task NavigateAsync(this WebBrowser @this, string url)
{
  var tcs = new TaskCompletionSource();
  WebBrowserDocumentCompletedEventHandler subscription = null;
  subscription = (_, args) =>
  {
    @this.DocumentCompleted -= subscription;
    tcs.TrySetResult(args.Url.ToString());
  };
  @this.DocumentCompleted += subscription;
  @this.Navigate(url);
  return tcs.Task;
}

Second part: a new Task NavAjaxAsync to run the tip for AJAX (based on Noseratio's code)

public static async Task NavAjaxAsync(this WebBrowser @this)
{
  // get the root element
  var documentElement = @this.Document.GetElementsByTagName("html")[0];

  // poll the current HTML for changes asynchronosly
  var html = documentElement.OuterHtml;

  while (true)
  {
    // wait asynchronously
    await Task.Delay(POLL_DELAY);

    // continue polling if the WebBrowser is still busy
    if (webBrowser.IsBusy)
      continue;

    var htmlNow = documentElement.OuterHtml;
    if (html == htmlNow)
      break; // no changes detected, end the poll loop

    html = htmlNow;
  }

  return @this.Document.Url.ToString();
}

Third part: a new Task NavAndAjaxAsync to get the navigation and the AJAX

public static async Task NavAndAjaxAsync(this WebBrowser @this, string url)
{
  await @this.NavigateAsync(url);
  await @this.NavAjaxAsync();
}

Fourth and last part: the updated Task GetUrlAsync from Stephen with Noseratio's code for AJAX

async Task GetUrlAsync(string url)
{
  using (var wb = new WebBrowser())
  {
    var navigate = wb.NavAndAjaxAsync(url);
    var timeout = Task.Delay(TimeSpan.FromSeconds(5));
    var completed = await Task.WhenAny(navigate, timeout);
    if (completed == navigate)
      return await navigate;
    return null;
  }
}

I'd like to know if this is the right approach.