HTML agility pack - removing unwanted tags without removing content?

Question

HTML agility pack - removing unwanted tags without removing content?

c# html-agility-pack

Question

I've seen a few related questions out here, but they don’t exactly talk about the same problem I am facing.

I want to use the HTML Agility Pack to remove unwanted tags from my HTML without losing the content within the tags.

So for instance, in my scenario, I would like to preserve the tags "b", "i" and "u".

And for an input like:

my paragraph <div>and my div</div> are italic and bold

The resulting HTML should be:

my paragraph and my div are italic and bold

I tried using HtmlNode's Remove method, but it removes my content too. Any suggestions?

Mathias Lykkegaard Lorenzen

How to recursively remove a given list of unwanted html tags from an html string

I took @mathias answer and improved his extension method so that you can supply a list of tags to exclude as a List<string> (e.g. {"a","p","hr"}). I also fixed the logic so that it works recursively properly:

public static string RemoveUnwantedHtmlTags(this string html, List<string> unwantedTags)
    {
        if (String.IsNullOrEmpty(html))
        {
            return html;
        }

        var document = new HtmlDocument();
        document.LoadHtml(html);

        HtmlNodeCollection tryGetNodes = document.DocumentNode.SelectNodes("./*|./text()");

        if (tryGetNodes == null || !tryGetNodes.Any())
        {
            return html;
        }

        var nodes = new Queue<HtmlNode>(tryGetNodes);

        while (nodes.Count > 0)
        {
            var node = nodes.Dequeue();
            var parentNode = node.ParentNode;

            var childNodes = node.SelectNodes("./*|./text()");

            if (childNodes != null)
            {
                foreach (var child in childNodes)
                {
                    nodes.Enqueue(child);                       
                }
            }

            if (unwantedTags.Any(tag => tag == node.Name))
            {               
                if (childNodes != null)
                {
                    foreach (var child in childNodes)
                    {
                        parentNode.InsertBefore(child, node);
                    }
                }

                parentNode.RemoveChild(node);

            }
        }

        return document.DocumentNode.InnerHtml;
    }

theyetiman

View more on Stack Overflow

Mathias Lykkegaard Lorenzen · Accepted Answer · 11/12/2016 12:37:12 AM

I wrote an algorithm based on Oded's suggestions. Here it is. Works like a charm.

It removes all tags except strong, em, u and raw text nodes.

internal static string RemoveUnwantedTags(string data)
{
    if(string.IsNullOrEmpty(data)) return string.Empty;

    var document = new HtmlDocument();
    document.LoadHtml(data);

    var acceptableTags = new String[] { "strong", "em", "u"};

    var nodes = new Queue<HtmlNode>(document.DocumentNode.SelectNodes("./*|./text()"));
    while(nodes.Count > 0)
    {
        var node = nodes.Dequeue();
        var parentNode = node.ParentNode;

        if(!acceptableTags.Contains(node.Name) && node.Name != "#text")
        {
            var childNodes = node.SelectNodes("./*|./text()");

            if (childNodes != null)
            {
                foreach (var child in childNodes)
                {
                    nodes.Enqueue(child);
                    parentNode.InsertBefore(child, node);
                }
            }

            parentNode.RemoveChild(node);

        }
    }

    return document.DocumentNode.InnerHtml;
}

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