// @nuget: HtmlAgilityPack

#nullable enable

​

using HtmlAgilityPack;

using System.Net;

using System.Collections.Generic;

using System;

​

public static class Program

{

    public static void Main()

    {

        // Load

        var html = "<p class=\"test\"><span class=\"text\">Hola, soy Carlos. </br> Encantado <a href=\"#popup\">de ayudarte</a>.</span></p></br>";

​

        string x = html.RemoveHtmlTags();

        Console.WriteLine(x);

    }

    public static string RemoveHtmlTags(this string html)

    {

        if (string.IsNullOrEmpty(html))

            return html;

​

        var doc = new HtmlAgilityPack.HtmlDocument();

        doc.LoadHtml(html);

​

        if (doc.DocumentNode == null || doc.DocumentNode.ChildNodes == null)

        {

            return WebUtility.HtmlDecode(html);

        }

​

        List<string> splitText = new();

​

        foreach (var node in doc.DocumentNode.ChildNodes)

        {

            List<string> nodeElements = SplitNodeElements(node);

            splitText.AddRange(nodeElements);

        }

​

        string result = string.Join("", splitText.ToArray());

        return WebUtility.HtmlDecode(result);

    }

​

    public static string GetOpeningTag(HtmlNode node, HtmlNode root)

    {

        return root.OuterHtml[node.OuterStartIndex..node.InnerStartIndex];

    }

​

    public static string GetClosingTag(HtmlNode node, HtmlNode root)

    {

        return root.OuterHtml[(node.InnerStartIndex + node.InnerLength)..(node.OuterStartIndex + node.OuterLength)];

    }

​

    public static List<string> SplitNodeElements(HtmlNode node, HtmlNode? root = null)

    {

        List<string> splitNode = new();

​

        // any text (i.e. "Hola")

        if (node.NodeType == HtmlNodeType.Text)

        {

            splitNode.Add(node.InnerText);

        }

​

        // tags without children (i.e., </br>)

        if (node.NodeType == HtmlNodeType.Element && !node.HasChildNodes)

        {

            splitNode.Add(node.OuterHtml);

        }

​

        if (node.NodeType == HtmlNodeType.Element && node.HasChildNodes)

        {

            splitNode.Add(GetOpeningTag(node, root ?? node));

            foreach (var child in node.ChildNodes)

            {

                splitNode.AddRange(SplitNodeElements(child, root ?? node));

            }

            splitNode.Add(GetClosingTag(node, root ?? node));

        }

​

        return splitNode;

    }

}