get value from html

Question

I'm fairly new to C#, and I'm trying to get a level from an in-browser game. This is the code I used and it came with an error

"Object reference not set to an instance of an object"

HtmlElementCollection elmnt = webBrowser1.Document
                                         .GetElementById("levelFrontTopArea")
                                         .GetElementsByTagName("value");
levellabel.Text = elmnt[0].InnerText;

Below I will show you the HTML code:

<div class="levelFrontTopArea">
   <a style="text-decoration:none" href="/profile.php">7</a>
</div>

While he is getting a `NullReference` exception, its only because he is trying to get a class element that doesnt have an id. The question is actually about how to get a class element. — crthompson, Dec 17 '13 at 20:58

crthompson · Accepted Answer · 2013-12-15T20:38:20.167

2

If you want to get an element by class you can loop through the div tags.

static IEnumerable<HtmlElement> ElementsByClass(HtmlDocument doc, string className)
{
  foreach (HtmlElement e in doc.All)
    if (e.GetAttribute("className") == className)
      yield return e;
}

You can call it like this:

var elmnt = ElementsByClass(webBrowser1.Document, "levelFrontTopArea");
levellabel.Text = elmnt.FirstOrDefault().InnerText;

edited Dec 15 '13 at 20:38

answered Dec 15 '13 at 04:25

crthompson

15,653
6
58
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Cannot apply indexing with [] to an expression of type 'System.Collections.Generic.IEnumerable – Tooproforyahoo Dec 15 '13 at 04:36
Oops, just copied your code on that, you can get the first element by using `FirstOrDefault` Because the method returns an IEnumerable, you can use it in a foreach as well. – crthompson Dec 15 '13 at 20:40

charlieparker · Answer 2 · 2013-12-15T04:38:02.277

0

You're using GetElementByID, but your div has no ID. Try changing your HTML to:

<div ID="levelFrontTopArea" class="levelFrontTopArea">
  <a style="text-decoration:none" href="/profile.php">7</a>
</div>

edited Dec 15 '13 at 04:38

answered Dec 15 '13 at 04:06

charlieparker

186
1
8

I cant change the code from the source If its just reading it, Right? – Tooproforyahoo Dec 15 '13 at 04:13
I'm not sure what you mean. Did you write the html yourself? Or is it generated by something? – charlieparker Dec 15 '13 at 04:19
Well then my solution won't work unless you're able to change the code that generates the html so that it gives it an ID. You could use getElementsByClassName. – charlieparker Dec 15 '13 at 04:24
There is only GetElementByTagName – Tooproforyahoo Dec 15 '13 at 04:25
OK. I think you need to change what you put in GetElementsByTagName too. Make it GetElementsByTagName("a") – charlieparker Dec 15 '13 at 04:27
Do I need to add a Using System.? – Tooproforyahoo Dec 15 '13 at 04:30
I have never seen a GetElementsByClassName method in c#. You can [write one](http://robertnyman.com/2008/05/27/the-ultimate-getelementsbyclassname-anno-2008/) however. – crthompson Dec 15 '13 at 04:35
Yeah, there isn't one, I was thinking of javascript. You should use @paqogomez 's answer. – charlieparker Dec 15 '13 at 04:36
I get the error Cannot apply indexing with [] to an expression of type 'System.Collections.Generic.IEnumerable with the code and the call.. – Tooproforyahoo Dec 15 '13 at 05:00

get value from html

2 Answers2