HtmlFilter.cs

        public static string FiltrarConteudoHTML(string sTexto) {
            var textOnly = sTexto;
            var output = new StringBuilder();
            var htmlDoc = new HtmlDocument();
            try {
                htmlDoc.LoadHtml(sTexto);

                htmlDoc.DocumentNode.Descendants()
                .Where(n => n.Name == "script" || n.Name == "comment" || n.Name == "div")
                .ToList()
                .ForEach(n => {
                    if (!n.InnerText.StartsWith("DOCTYPE") && n.Name != "div"
                        || n.Attributes["id"]?.Value == "header")
                            n.Remove();
                });

                var linesCount = 0;
                var text = htmlDoc.DocumentNode.SelectNodes("//body//text()").Select(node => node.InnerText);
                foreach (string line in text) {
                    var result = Regex.Replace(line, @"\r\n?|\n", string.Empty);
                    if(linesCount < 2 && !string.IsNullOrEmpty(result) && !string.IsNullOrWhiteSpace(result)) {
                        output.AppendLine(result);
                        linesCount++;
                    }
                }

                textOnly = HttpUtility.HtmlDecode(output.ToString());
            } catch (Exception ex) {
                TratarErro(ex,$"{nameof(Utils)}.{nameof(FiltrarConteudoHTML)}");
            }

            return textOnly;
        }