How to extract one word or some words from an HTML page C#

Question

Here I'm trying to extract one word from an HTML page. For example, there are two textboxes (1 and 2). now I'm trying to give stackoverflow question ID on textbox1 and get "asked" value on textbox2. For example, if I give 36 on textbox1 this should give me "9 years, 4 months ago" on textbox2. WebClient webpage = new WebClient(); String html = webpage.DownloadString("https://stackoverflow.com/questions/" + textBox1.Text); MatchCollection match = Regex.Matches(html, FILTERHERE, RegexOptions.Singleline); The problem is I don't know how to filter my output (FILTERHERE)? Also how can I send my output into textbox2?

Using Regex on html is a [bad idea](https://stackoverflow.com/a/1732454/) — Aleks Andreev, Dec 16 '17 at 08:45
@Leviathan, the xpath is `//*[@id='qinfo']//td[./p[@class='label-key' and text()='asked']]/following-sibling::td//b/text()`. In the future consider using HtmlAgilityPack instead of RegEx. — derloopkat, Dec 16 '17 at 21:30

derloopkat · Accepted Answer · 2017-12-18T11:23:16.853

With HtmlAgilityPack.

string url = "https://stackoverflow.com/questions/";
var web = new HtmlWeb();
var doc = web.Load(url + textBox1.Text); //the text is "36"
var tag = doc.DocumentNode.SelectSingleNode("//*[@id='qinfo']//td[./p[@class='label-key' and text()='asked']]/following-sibling::td//b");
textBox2.Text = tag.InnerText;

If you don't know XPath, there are browser extensions for Chrome and Firefox that gets the XPath of any Html tag for you (I personally write them manually to make them less sensitive to changes on page structure).

Daniel Dušek · Answer 2 · 2017-12-17T17:20:17.820

2

With Windows Forms applicationWebBrowser control canbe used wthich wpapps the mshtml library and exposes managed HTML DOM. Example of function which retrieves the asked text:

private static string GetAskedText(HtmlDocument doc)
{
    if (doc == null)
        return "document-null";
    IEnumerable<mshtml.HTMLDivElement> divs = doc.GetElementsByTagName("div")
        .OfType<HtmlElement>()
        .Select(e => e.DomElement as mshtml.HTMLDivElement);
    foreach (var div in divs)
    {
        if (string.IsNullOrWhiteSpace(div?.className))
            continue;
        if (div.className.Trim().ToLower() != "user-info")
            continue;
        var spans = div.getElementsByTagName("span").OfType<mshtml.HTMLSpanElement>();
        foreach (var span in spans)
        {
            if (string.IsNullOrWhiteSpace(span?.className))
                continue;
            if (span.className == "relativetime")
            {
                return span.innerText;
            }
        }
    }

    return "not-found";
}

Complete example with Windows Forms application can be downloaded from my dropbox.

edited Dec 17 '17 at 17:20

answered Dec 16 '17 at 20:12

Daniel Dušek

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Thanks but it's a console application. I asked about windows form application. – Leviathan Dec 16 '17 at 20:35
Windows Forms? That is just a very small difference. The function `GetAsked` remains the same. – Daniel Dušek Dec 16 '17 at 20:36
Yes:P but it's not the same btw – Leviathan Dec 16 '17 at 20:44
The Windows Forms version can be downloaded from my dropbox, see link in edited answer. HTH – Daniel Dušek Dec 16 '17 at 21:07

How to extract one word or some words from an HTML page C#

2 Answers2