C# HtmlDecode Specific tags only

Question

I have a large htmlencoded string and i want decode only specific whitelisted html tags.

Is there a way to do this in c#, WebUtility.HtmlDecode() decodes everything.

Answer 1

Or you could use HtmlAgility with a black list or white list based on your requirement. I'm using black listed approach. My black listed tag is store in a text file, for example "script|img"

public static string DecodeSpecificTags(this string content, List blackListedTags)
    {
        if (string.IsNullOrEmpty(content))
        {
            return content;
        }
        blackListedTags = blackListedTags.Select(t => t.ToLowerInvariant()).ToList();
        var decodedContent = HttpUtility.HtmlDecode(content);
        var document = new HtmlDocument();
        document.LoadHtml(decodedContent);
        decodedContent = blackListedTags.Select(blackListedTag => document.DocumentNode.Descendants(blackListedTag))
                .Aggregate(decodedContent,
                    (current1, nodes) =>
                        nodes.Select(htmlNode => htmlNode.WriteTo())
                            .Aggregate(current1,
                                (current, nodeContent) =>
                                    current.Replace(nodeContent, HttpUtility.HtmlEncode(nodeContent))));
        return decodedContent;
    }