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.NET Forum / ASP.NET / Web Services / November 2007Parsing HTML
Hi I want to parse a web page (in a web service) and retrive some of its information. I googled the MSDN and found a walkthrough (How to: Create Web Services That Parse the Contents of a Web Page) but the walkthrogh is a little complex and the writer did not completly describe all the aspects of the solution. Could any one elaborate on this walkthrough? Or direct me to another (or better) way to deal with such a problem. Thanks in advance. How about using the W3C Document Object Model, which was designed to do just what you are trying to do? > Hi > I want to parse a web page (in a web service) and retrive some of its [quoted text clipped - 8 lines] > > Thanks in advance. I want to write a web service that extracts some information from a web page and use that web service in a windows application. I think the usual solution for parsing is a little bit slow and costs too much (getting HTML code and finding the keys using loops). I want to know if there is any possible way in .NET to simply extract those information (for example a method that returns every HTML tag of the web page with its value)? The process time of the web service is very important for me. Thanks in advance. > How about using the W3C Document Object Model, which was designed to do just > what you are trying to do? [quoted text clipped - 11 lines] > > > > Thanks in advance. I don't know where you have gotten your information, but this is exactly what the DOM is for. >I want to write a web service that extracts some information from a web >page [quoted text clipped - 28 lines] >> > >> > Thanks in advance. >I don't know where you have gotten your information, but this is exactly >what the DOM is for. Scott, I used this approach with a Windows Forms application back in 2001, with .NET 1.0. It worked, but was a bit clumsy, and it was time-consuming. I used the ActiveX Internet Browser control to load the page I was interested in, and once the page was loaded, I could access the DOM from C# code. Did you have a different technique in mind when you talk about the DOM? Perhaps a faster technique would be to use regular expressions to parse the HTML and find what you're looking for. John What I had in mind was, if the HTML in question was well-formed (XHTML), you could just load it into an XMLDocument (from a string) object and use the XML DOM to parse from there. >>I don't know where you have gotten your information, but this is exactly >>what the DOM is for. [quoted text clipped - 12 lines] > > John Can you give a sample code for loading XHTML to a XMLDocument? > What I had in mind was, if the HTML in question was well-formed (XHTML), you > could just load it into an XMLDocument (from a string) object and use the [quoted text clipped - 16 lines] > > > > John Well, XHTML is XML, so you'd really be loading XML into an XMLDocument, but once it's loaded, you can parse out whatever you like using the DOM. Dim xmlDoc As New System.XML.XMLDocument() 'You can load the XML in one of two ways... 'docPath represents a path to an file containing the XML xmlDoc.Load(docPath) 'or 'Here you can load a string directly xmlDoc.LoadXML(string) 'Example of getting all the paragraph tags and then the text of the first one using the DOM... dim theParagraphs As XMLNodeList = xmlDoc.GetElementsByTagName("P") dim firstParagraphText As String = theParagraphs(0).Text -Scott > Can you give a sample code for loading XHTML to a XMLDocument? > [quoted text clipped - 22 lines] >> > >> > John > What I had in mind was, if the HTML in question was well-formed (XHTML), > you could just load it into an XMLDocument (from a string) object and use > the XML DOM to parse from there. That works well for XHTML. The problem is that most web sites are still using HTML, which is not well-formed XML. John But, we're not talking about most web pages. We are talking about a particular page that is being used with a web service. In other words, it's part of the OP's applicaiton, which he should have some control over. >> What I had in mind was, if the HTML in question was well-formed (XHTML), >> you could just load it into an XMLDocument (from a string) object and use [quoted text clipped - 4 lines] > > John > But, we're not talking about most web pages. We are talking about a > particular page that is being used with a web service. In other words, > it's part of the OP's applicaiton, which he should have some control over. Sorry, I didn't recall that he said it was his application. I assumed he was scraping from somebody else's application. Even though it's his, there may be reasons why he can't guarantee that the page he needs will be XHTML and will be guaranteed to remain XHTML. John An answer is HtmlAgilityPack (www.codeplex.com/htmlagilitypack). > Hi > I want to parse a web page (in a web service) and retrive some of its [quoted text clipped - 6 lines] > > Thanks in advance. 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