Sirefinity Async Mvc Script

SfCustomHtmlHelpers.cs

using System.Linq;
using System.Web.Mvc;
using Telerik.Sitefinity.Frontend.Mvc.Helpers;
using Telerik.Sitefinity.Modules.Pages;

namespace SitefinityWebApp.Custom
{
    public static class SfCustomHtmlHelpers
    {
        public static MvcHtmlString ScriptAsync(this HtmlHelper helper, ScriptRef scriptReference)
        {
            var markup = helper.Script(scriptReference, null, false, true);
            //markup = new MvcHtmlString(markup.ToHtmlString().Replace("src", "defer src"));

            var doc = new System.Xml.XmlDocument();
            doc.LoadXml(markup.ToHtmlString());
            var tagBuilder = new TagBuilder("script");
            if (doc.DocumentElement == null) return new MvcHtmlString(tagBuilder.ToString(TagRenderMode.EndTag));

            tagBuilder.MergeAttributes(
                doc.DocumentElement.Attributes
                .Cast<System.Xml.XmlAttribute>()
                .ToDictionary(x => x.Name, x => x.Value));

            tagBuilder.Attributes["async"] = "";
            tagBuilder.InnerHtml = doc.DocumentElement.InnerXml;

            return new MvcHtmlString(tagBuilder.ToString(TagRenderMode.EndTag));
        }

        public static MvcHtmlString ScriptAsync(this HtmlHelper helper, string scriptPath)
        {
            var markup = helper.Script(scriptPath, null, false, true);

            var doc = new System.Xml.XmlDocument();
            doc.LoadXml(markup.ToHtmlString());
            var tagBuilder = new TagBuilder("script");
            if (doc.DocumentElement == null) return new MvcHtmlString(tagBuilder.ToString(TagRenderMode.EndTag));

            tagBuilder.MergeAttributes(
                doc.DocumentElement.Attributes
                    .Cast<System.Xml.XmlAttribute>()
                    .ToDictionary(x => x.Name, x => x.Value));
            tagBuilder.Attributes["async"] = "";
            tagBuilder.InnerHtml = doc.DocumentElement.InnerXml;

            return new MvcHtmlString(tagBuilder.ToString(TagRenderMode.EndTag));
        }
    }
}