Javascript defer by script file or script block (for MVC using Razor view engine)

JavaScriptInclude_Rz.cs

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.Mvc;
using System.Web.WebPages;

namespace Web.Extensions {
	public static class JavascriptIncludeExtensions {
		private const string JscriptIncludeViewdata = "__jsrq";
		private const string JscriptDeferRazorViewdata = "__jsdfrz";

		/// <summary>
		/// Include a javascript url to be written by the RenderScripts method.
		/// Url will be included exactly once no matter how many times this method is called.
		/// </summary>
		public static void DeferScript (this HtmlHelper html, string scriptLocation) {
			string jsTag = "<script type=\"text/javascript\" src=\"" + scriptLocation + "\"></script>";

			var jscripts = html.ViewContext.TempData[JscriptIncludeViewdata] as List<string> ?? new List<string>();
			if (!jscripts.Contains(jsTag)) jscripts.Add(jsTag);
			html.ViewContext.TempData[JscriptIncludeViewdata] = jscripts;
		}

		/// <summary>
		/// Defer a script block (or any other HTML string) until RenderScripts is called.
		/// Defered blocks always render after included script sources.
		/// Call like: @Html.Defer(@&lt;script&gt;...&lt;/script&gt;)
		/// </summary>
		public static IHtmlString Defer (this HtmlHelper html, Func<int, HelperResult>  script) {
			var jsActions = html.ViewContext.TempData[JscriptDeferRazorViewdata] as List<Func<int, HelperResult>> ?? new List<Func<int, HelperResult>>();
			jsActions.Add(script);
			html.ViewContext.TempData[JscriptDeferRazorViewdata] = jsActions;
			return new HtmlString("");
		}

		/// <summary>
		/// Render all defered scripts at this point. Defered scripts list will be reset.
		/// </summary>
		public static HelperResult RenderDeferred (this HtmlHelper html) {
			var jscripts = html.ViewContext.TempData[JscriptIncludeViewdata] as List<string>;
			var jsActions = html.ViewContext.TempData[JscriptDeferRazorViewdata] as List<Func<int, HelperResult>>;

			html.ViewContext.TempData[JscriptDeferViewdata] = new List<Func<int, HelperResult>>();
			html.ViewContext.TempData[JscriptIncludeViewdata] = new List<string>();
			return new HelperResult(writer =>
			{
				if (jscripts != null) {
					writer.Write(string.Join("\r\n", jscripts.ToArray()));
				}
				if (jsActions != null) foreach (var action in jsActions) { action(0).WriteTo(writer); }
			});
		}
	}
}