Parsing form with HTML Agility Pack

问题

I'm trying to extract all input elements from a form. When I parse the following form:

<form>
<input name='test1' type='text'>
<input name='test2' type='text'>
<input name='test3' type='text'>
</form>

everything worked perfectly, HTML Agility Pack was able to detect the input elements in the form but if it has a div parent node like the following, it will not be detected.

<form>
<div><input name='test1' type='text'></div>
<div><input name='test2' type='text'></div>
<div><input name='test3' type='text'></div>
</form>

I'm using the following code

HtmlNode.ElementsFlags.Remove("form");

foreach (HtmlAgilityPack.HtmlNode node in postForm.Elements("input"))
{
    HtmlAgilityPack.HtmlAttribute valueAttribute = node.Attributes["value"];
}

Can anyone tell me what went wrong? Thanks

回答1:

HtmlNode.Elements method gets matching first generation child nodes matching name. After you put your inputs inside a <div> tag they become the second generation child nodes for the form element.

To make your code work use HtmlNode.Descendants method which gets all descendant nodes with matching name:

foreach (HtmlAgilityPack.HtmlNode node in postForm.Descendants("input"))
{
   HtmlAgilityPack.HtmlAttribute valueAttribute = node.Attributes["value"];
}

回答2:

I don't remember what does ".Elements()" do, but I assume that it just returns the children nodes... and in your case the direct childs of your Form are divs.

You can use XPATH to have a little more control:

.SelectNodes("//form/div/input")

This will return a list of input nodes in a form, knowing that the input is withing a div tag.

Here you can see an XPATH TUTORIAL with examples.

回答3:

Use Descendants() instead of Elements() - the later only works on direct children but your input elements are nested within divs:

 foreach (HtmlAgilityPack.HtmlNode node in postForm.Descendants("input"))
 {
     HtmlAgilityPack.HtmlAttribute valueAttribute = node.Attributes["value"];
 }

来源：https://stackoverflow.com/questions/9889404/parsing-form-with-html-agility-pack

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html-agility-pack