HtmlStringExtensions.cs

HtmlStringExtensions.cs

 public static class HtmlStringExtensions
    {
        public static bool IsNullOrWhiteSpace(this IHtmlString htmlString)
        {
            return htmlString == null || string.IsNullOrWhiteSpace(htmlString.ToHtmlString());
        }

        public static HtmlString AddClass(this IHtmlString html, string css)
        {
            return html.UpdateElement(node => node.AddClass(css));
        }

        public static HtmlString AddClassToOuterParagraphTag(this IHtmlString html, string css)
        {
            return html.UpdateElement("//p", node => node.AddClass(css));
        }

        public static HtmlString RemoveOuterParagraphTag(this IHtmlString html)
        {
            var doc = GetHtmlDocument(html);
            var node = doc?.DocumentNode.ChildNodes?.FirstOrDefault(n => n.NodeType != HtmlNodeType.Text);
            return new HtmlString(node?.InnerHtml.Trim());
        }

        public static HtmlString UpdateElement(this IHtmlString html, Action<HtmlNode> updateFunc)
        {
            var doc = GetHtmlDocument(html);
            var node = doc?.DocumentNode.ChildNodes?.FirstOrDefault(n => n.NodeType != HtmlNodeType.Text);
            if (node != null) 
                updateFunc(node);

            return new HtmlString(doc?.DocumentNode.OuterHtml);
        }

        public static HtmlString UpdateElement(this IHtmlString html, string tagPath, Action<HtmlNode> updateFunc)
        {
            var doc = GetHtmlDocument(html);
            var node = doc?.DocumentNode.SelectSingleNode(tagPath);
            updateFunc(node);

            return new HtmlString(doc?.DocumentNode.OuterHtml);
        }

        private static HtmlDocument GetHtmlDocument(IHtmlString html)
        {
            var content = html.ToString();
            if (content.IsNullOrWhiteSpace())
                return null;

            var doc = new HtmlDocument();
            doc.LoadHtml(content);

            return doc;
        }
 }