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POParsing html -> xml and querying with Xpath
 

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    <p>I want to parse a html page to get some data. First, I convert it to XML document using <em>SgmlReader</em>. Then, I load the result to XMLDocument and then navigate through XPath:</p> <pre><code>//contains html document var loadedFile = LoadWebPage(); ... Sgml.SgmlReader sgmlReader = new Sgml.SgmlReader(); sgmlReader.DocType = "HTML"; sgmlReader.WhitespaceHandling = WhitespaceHandling.All; sgmlReader.CaseFolding = Sgml.CaseFolding.ToLower; sgmlReader.InputStream = new StringReader(loadedFile); XmlDocument doc = new XmlDocument(); doc.PreserveWhitespace = true; doc.XmlResolver = null; doc.Load(sgmlReader); </code></pre> <p>This code works fine for most cases, except on this site - <a href="http://www.arrow.com/" rel="nofollow noreferrer">www.arrow.com</a> (try to search something like OP295GS). I can get a table with result using the following XPath:</p> <pre><code>var node = doc.SelectSingleNode(".//*[@id='results-table']"); </code></pre> <p>This gives me a node with several child nodes:</p> <pre><code>[0] {Element, Name="thead"} [1] {Element, Name="tbody"} [2] {Element, Name="tbody"} FirstChild {Element, Name="thead"} </code></pre> <p>Ok, let's try to get some child nodes using XPath. But this doesn't work:</p> <pre><code>var childNodes = node.SelectNodes("tbody"); //childnodes.Count = 0 </code></pre> <p>This also:</p> <pre><code>var childNode = node.SelectSingleNode("thead"); // childNode = null </code></pre> <p>And even this:</p> <pre><code>var childNode = doc.SelectSingleNode(".//*[@id='results-table']/thead") </code></pre> <p>What can be wrong in Xpath queries?</p> <hr> <p>I've just tried to parse that HTML page with <em>Html Agility Pack</em> and my XPath queries work good. But my application use XmlDocument inside, <em>Html Agility Pack</em> doesn't suit me.</p> <hr> <p>I even tried the following trick with <em>Html Agility Pack</em>, but Xpath queries doesn't work also:</p> <pre><code>//let's parse and convert HTML document using HTML Agility Pack and then load //the result to XmlDocument HtmlDocument xmlDocument = new HtmlDocument(); xmlDocument.OptionOutputAsXml = true; xmlDocument.Load(new StringReader(webPage)); XmlDocument document = new XmlDocument(); document.LoadXml(xmlDocument.DocumentNode.InnerHtml); </code></pre> <p>Perhaps, web page contains errors (not all tags are closed and so on), but in spite of this I can see child nodes (through Quick Watch in Visual Studio), but cannot access them through XPath.</p> <hr> <p>My XPath queries works correctly in Firefox + FirePath + XPather plugins, but don't work in .net XmlDocument :(</p>
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    1. CO+1 for a good question, and for parsing HTML with the Agility Pack and XML parsers rather than regex.
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    2. COHTML Agility Pack is easy to use, but it has it's own data types, what can be a problem when integrating in an existing logic.
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