I'm trying to figure out how to grab DOM elements from a webpage. Here is the function I'm using:
private void processHTML(String htmlContent)
{
IHTMLDocument2 htmlDocument = (IHTMLDocument2)new mshtml.HTMLDocument();
htmlDocument.write(htmlContent);
IHTMLElementCollection allElements = htmlDocument.all;
webBrowser1.DocumentText = allElements.item("storytext").innerHTML;
textBox2.Text = allElements.item("chap_select").length.ToString();
}
If I set a breakpoint at either of the last two lines and then check the allElements collection, I'm able to find the SELECT element. It correctly shows the ID as being chap_select and the length property shows 13 for the particular document that is being passed. For some reason the length that is being put into the textBox2 field is 2, however.
Any suggestions on what I'm doing wrong here? I've spent several hours trying to figure this out, but have not been able to find any code samples of somebody trying to grab this property of a SELECT.
Instead of using IHTMLDocument2 and mshtml.HTMLDocument I suggest using the much easier to work with HTML Agility Pack.
What is exactly the Html Agility Pack (HAP)?
This is an agile HTML parser that builds a read/write DOM and supports plain XPATH or XSLT (you actually don't HAVE to understand XPATH nor XSLT to use it, don't worry...). It is a .NET code library that allows you to parse "out of the web" HTML files. The parser is very tolerant with "real world" malformed HTML. The object model is very similar to what proposes System.Xml, but for HTML documents (or streams).
Something like (untested):
var doc = new HtmlDocument();
doc.LoadHtml(htmlContent);
textBox2.Text = doc.DocumentNode
.SelectNodes("//select[#id='chap_select']/option").Count().ToString();
Related
I have this from html page source
<h5 class="icn-venue">Tavernita</h5>
There are say 10 values like this between these tags on the page source.
I want to extract value between "h5" tags. Class="icn-venue" remains same for all values.
I tried splitting the tag and then storing but the code doesnt seem to work.
You can do it like this using htmlAgilityPack:
HtmlDocument doc = new HtmlDocument();
doc.Load(yourStream);
List<string> lst=doc.DocumentNode.SelectNodes("//h5[class='icn-venue']")
.Select(x=>x.InnerHtml)
.ToList();
HTML Agility Pack is a great tool for manipulating and working with HTML: http://htmlagilitypack.codeplex.com/
It could at least make grabbing the values you need and doing the replaces a little easier.
Contains links to using the HTML Agility Pack: How to use HTML Agility pack
I have a string:
<div class="className1234"><p>Some html</p></div>
From this string, I would like to get <p>Some html</p> i.e. I would like to remove the surrounding div tags based on the fact that it's class contains 'className'.
What I've Tried
What I've tried works, but it's cludgey - and I know there'll be a better alternative like regex or something. What I currently do is chain a series of substring(), indexof() and replace() calls to strip out the divs.
EDIT: I've used the phrase 'innerhtml' because I'd like to think there's a library out there somewhere that would allow me to manipulate a string with regard to the tags within it.
PLEASE NOTE: There's no JQuery involved in this. It's all server-side C#.
(See tags)
I would suggest Html Agility Pack, it's designed to allow operations on html documents, kind of like the builtin support for XML in the framework.
It might be overkill, but it will get the work done, easily, and you won't have to care about bad html
How about:
XmlDocument doc = new XmlDocument();
doc.LoadXml(divStr);
// classAtr will be null if the root is not a div with a class with the value className1234
XmlNode classAtr = doc.SelectSingleNode("/div/#class[contains(., 'className1234')]");
string result = classAtr != null ? doc.DocumentElement.InnerXml : divStr;
Whenever you need to manipulate HTML, you should use a dedicated HTML parser/DOM library. One library I've found recommended here on StackOverflow for .Net is HTMLAgilityPack.
As others said HtmlAgilityPack is the best for html parsing, also be sure to download HAP Explorer from HtmlAgilityPack site, use it to test your selects, anyway this SelectNode command will get :
HtmlDocument doc = new HtmlDocument();
doc.Load(htmlFile);
var myNodes = doc.DocumentNode.SelectNodes("/div/#class[. = 'className1234']");
foreach (HtmlNode node in myNodes)
{
// you code
}
Knowing that I can't use HTMLAgilityPack, only straight .NET, say I have a string that contains some HTML that I need to parse and edit in such ways:
find specific controls in the hierarchy by id or by tag
modify (and ideally create) attributes of those found elements
Are there methods available in .net to do so?
HtmlDocument
GetElementById
HtmlElement
You can create a dummy html document.
WebBrowser w = new WebBrowser();
w.Navigate(String.Empty);
HtmlDocument doc = w.Document;
doc.Write("<html><head></head><body><img id=\"myImage\" src=\"c:\"/><a id=\"myLink\" href=\"myUrl\"/></body></html>");
Console.WriteLine(doc.Body.Children.Count);
Console.WriteLine(doc.GetElementById("myImage").GetAttribute("src"));
Console.WriteLine(doc.GetElementById("myLink").GetAttribute("href"));
Console.ReadKey();
Output:
2
file:///c:
about:myUrl
Editing elements:
HtmlElement imageElement = doc.GetElementById("myImage");
string newSource = "d:";
imageElement.OuterHtml = imageElement.OuterHtml.Replace(
"src=\"c:\"",
"src=\"" + newSource + "\"");
Console.WriteLine(doc.GetElementById("myImage").GetAttribute("src"));
Output:
file:///d:
Assuming you're dealing with well formed HTML, you could simply treat the text as an XML document. The framework is loaded with features to do exactly what you're asking.
http://msdn.microsoft.com/en-us/library/system.xml.xmldocument.aspx
Aside from the HTML Agility Pack, and porting HtmlUnit over to C#, what sounds like solid solutions are:
Most obviously - use regex. (System.Text.RegularExpressions)
Using an XML Parser. (because HTML is a system of tags treat it like an XML document?)
Linq?
One thing I do know is that parsing HTML like XML may cause you to run into a few problems. XML and HTML are not the same. Read about it: here
Also, here is a post about Linq vs Regex.
You can look at how HTML Agility Pack works, however, it is .Net. You can reflect the assembly and see that it is using the MFC and could be reproduced if you so wanted, but you'd be doing nothing more than moving the assembly, not making it any more .Net.
I want to get text off of a webpage in C#.
I don't want to get the HTML, I want the real text off of the webpage. Like if I type "<b>cake</b>", I want the cake, not the tags.
Use the HTML Agility Pack library.
That's very fine library for parse HTML, for your requirement use this code:
HtmlAgilityPack.HtmlWeb web = new HtmlAgilityPack.HtmlWeb();
HtmlAgilityPack.HtmlDocument doc = web.Load("Yor Path(local,web)");
var result=doc.DocumentNode.SelectNodes("//body//text()");//return HtmlCollectionNode
foreach(var node in result)
{
string AchivedText=node.InnerText;//Your desire text
}
It depends. If your application downloads the webpage using a WebBrowser component, then that component will do the parsing for you automatically in the background (just like Internet Explorer). Just walk the DOM tree and extract the text you want. You will find HtmlElement.InnerText property especially useful :)
You can strip tags using regular expressions such as this one2 (a simple example):
// You can import System.Text.RegularExpressions for convenience, of course.
System.Text.RegularExpressions.Regex tag = new System.Text.RegularExpressions.Regex("\<.+?\>");
myHTML = tag.Replace(myHTML, String.Empty);
But if you need to retrieve large volumes of well-structured data, then you might be better off using an HTML library1. (If the webpage is XHTML, all the better - use the System.Xml classes.)
1 Like http://htmlagilitypack.codeplex.com/, for example.
2 This might have unintended side-effects if you're trying to get data out of JavaScript, or if the data is inside an element's attribute and includes angle brackets. You'll also need to accept escape sequences like &.
Can Html Agility Pack be used to parse an html string fragment?
Such As:
var fragment = "<b>Some code </b>";
Then extract all <b> tags? All the examples I seen so far have been loading like html documents.
If it's html then yes.
string str = "<b>Some code</b>";
// not sure if needed
string html = string.Format("<html><head></head><body>{0}</body></html>", str);
HtmlDocument doc = new HtmlDocument();
doc.LoadHtml(html);
// look xpath tutorials for how to select elements
// select 1st <b> element
HtmlNode bNode = doc.DocumentNode.SelectSingleNode("b[1]");
string boldText = bNode.InnerText;
I dont think this is really the best use of HtmlAgilityPack.
Normally I see people trying to parse large amounts of html using regular expressions and I point them towards HtmlAgilityPack but in this case I think it would be better to use a regex.
Roy Osherove has a blog post describing how you can strip out all the html from a snippet:
http://weblogs.asp.net/rosherove/archive/2003/05/13/6963.aspx
Even if you did get the correct xpath with Mika Kolari's sample this would only work for a snippet with a <b> tag in it and would break if the code changed.
This answer came up when I searched for the same thing. I don't know if the features have changed since it was answered but this below should be better.
$string = '<b>Some code </b>'
[HtmlAgilityPack.HtmlNode]::CreateNode($string)