remove html node from htmldocument :HTMLAgilityPack

Question

In my code, I want to remove the img tag which doesn't have src value. I am using HTMLAgilitypack's HtmlDocument object. I am finding the img which doesn't have src value and trying to remove it.. but it gives me error Collection was modified; enumeration operation may not execute. Can anyone help me for this? The code which I have used is:

foreach (HtmlNode node in doc.DocumentNode.DescendantNodes())
{
    if (node.Name.ToLower() == "img")
    {                            
           string src = node.Attributes["src"].Value;
           if (string.IsNullOrEmpty(src))
           {
               node.ParentNode.RemoveChild(node, false);    
           }
   }
   else
   {
             ..........// i am performing other operations on document
   }
}

Oleks · Accepted Answer · 2012-08-30 16:06:19Z

28

It seems you're modifying the collection during the enumeration by using HtmlNode.RemoveChild method.

To fix this you need is to copy your nodes to a separate list/array by calling e.g. Enumerable.ToList<T>() or Enumerable.ToArray<T>().

var nodesToRemove = doc.DocumentNode
    .SelectNodes("//img[not(string-length(normalize-space(@src)))]")
    .ToList();

foreach (var node in nodesToRemove)
    node.Remove();

If I'm right, the problem will disappear.

answered Aug 30, 2012 at 16:06

Oleks

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1 Comment

Oleks Over a year ago

@Piya, glad to hear that. But I think by using one xpath expression is easier to make your code more readable (just select all the nodes to remove with one expression).

Priya · Accepted Answer · 2012-08-31 05:51:13Z

12

What I have done is:

    List<string> xpaths = new List<string>();
    foreach (HtmlNode node in doc.DocumentNode.DescendantNodes())
    {
                        if (node.Name.ToLower() == "img")
                        {
                            string src = node.Attributes["src"].Value;
                            if (string.IsNullOrEmpty(src))
                            {
                                xpaths.Add(node.XPath);
                                continue;
                            }
                        }
    }

    foreach (string xpath in xpaths)
    {
            doc.DocumentNode.SelectSingleNode(xpath).Remove();
    }

edited Aug 31, 2012 at 5:51

answered Aug 31, 2012 at 5:46

Priya

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Comments

Krzysztof Radzimski · Accepted Answer · 2016-01-25 11:34:43Z

4

var emptyImages = doc.DocumentNode
 .Descendants("img")
 .Where(x => x.Attributes["src"] == null || x.Attributes["src"].Value == String.Empty)
 .Select(x => x.XPath)
 .ToList(); 

emptyImages.ForEach(xpath => { 
      var node = doc.DocumentNode.SelectSingleNode(xpath);
      if (node != null) { node.Remove(); }
    });

answered Jan 25, 2016 at 11:34

Krzysztof Radzimski

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Comments

MOHAMMAD · Accepted Answer · 2019-05-22 11:14:25Z

1

var emptyElements = doc.DocumentNode
    .Descendants("a")
    .Where(x => x.Attributes["src"] == null || x.Attributes["src"].Value == String.Empty)
    .ToList();

emptyElements.ForEach(node => {
    if (node != null){ node.Remove();}
});

answered May 22, 2019 at 11:14

MOHAMMAD

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1 Comment

double-beep Over a year ago

While this code may solve the question, including an explanation of how and why this solves the problem would really help to improve the quality of your post, and probably result in more up-votes. Remember that you are answering the question for readers in the future, not just the person asking now. Please edit your answer to add explanations and give an indication of what limitations and assumptions apply.

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