How to Timeout a request using Html Agility Pack

Question

I'm making a request to a remote web server that is currently offline (on purpose).

I'd like to figure out the best way to time out the request. Basically if the request runs longer than "X" milliseconds, then exit the request and return a null response.

Currently the web request just sits there waiting for a response.....

How would I best approach this problem?

Here's a current code snippet

    public JsonpResult About(string HomePageUrl)
    {
        Models.Pocos.About about = null;
        if (HomePageUrl.RemoteFileExists())
        {
            // Using the Html Agility Pack, we want to extract only the
            // appropriate data from the remote page.
            HtmlWeb hw = new HtmlWeb();
            HtmlDocument doc = hw.Load(HomePageUrl);
            HtmlNode node = doc.DocumentNode.SelectSingleNode("//div[@class='wrapper1-border']");

            if (node != null)
            { 
                about = new Models.Pocos.About { html = node.InnerHtml };
            }
                //todo: look into whether this else statement is necessary
            else 
            {
                about = null;
            }
        }

        return this.Jsonp(about);
    }

Answer 1

Retrieve your url web page through this method:

private static string retrieveData(string url)
    {
        // used to build entire input
        StringBuilder sb = new StringBuilder();

        // used on each read operation
        byte[] buf = new byte[8192];

        // prepare the web page we will be asking for
        HttpWebRequest request = (HttpWebRequest)
        WebRequest.Create(url);
        request.Timeout = 10; //10 millisecond
        // execute the request

        HttpWebResponse response = (HttpWebResponse)
        request.GetResponse();

        // we will read data via the response stream
        Stream resStream = response.GetResponseStream();

        string tempString = null;
        int count = 0;

        do
        {
            // fill the buffer with data
            count = resStream.Read(buf, 0, buf.Length);

            // make sure we read some data
            if (count != 0)
            {
                // translate from bytes to ASCII text
                tempString = Encoding.ASCII.GetString(buf, 0, count);

                // continue building the string
                sb.Append(tempString);
            }
        }
        while (count > 0); // any more data to read?

        return sb.ToString();
    }

And to use the HTML Agility pack and retrive the html tag like this:

public static string htmlRetrieveInfo()
    {
        string htmlSource = retrieveData("http://example.com/test.html");
        HtmlDocument doc = new HtmlDocument();
        doc.LoadHtml(htmlSource);
        if (doc.DocumentNode.SelectSingleNode("//body") != null)
        {
          HtmlNode node = doc.DocumentNode.SelectSingleNode("//body");
        }
        return node.InnerHtml;
    }

Answer 2

Html Agility Pack is open souce. Thats why you may modify source yurself. For first add this code to class HtmlWeb:

private int _timeout = 20000;

public int Timeout 
    { 
        get { return _timeout; } 
        set
        {
            if (_timeout < 1) 
                throw new ArgumentException("Timeout must be greater then zero.");
            _timeout = value;
        }
    }

Then find this method

private HttpStatusCode Get(Uri uri, string method, string path, HtmlDocument doc, IWebProxy proxy, ICredentials creds)

and modify it:

req = WebRequest.Create(uri) as HttpWebRequest;
req.Method = method;
req.UserAgent = UserAgent;
req.Timeout = Timeout; //add this

Or something like that:

htmlWeb.PreRequest = request =>
            {
                request.Timeout = 15000;
                return true;
            };