An IHttpActionResult that returns cached views with models requires RazorEngine

HtmlActionResult.cs

using System.Linq;
using Newtonsoft.Json;
using RazorEngine.Configuration;
using RazorEngine.Templating;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text.RegularExpressions;
using System.Threading;
using System.Threading.Tasks;
using System.Web.Http.Results;

namespace System.Web.Http.Results {

	public class HtmlActionResult : IHttpActionResult {

		private readonly string _template;
		private readonly dynamic _model;
		private readonly string _root;

		public HtmlActionResult(string name, dynamic model, string root = null) {

			_template = name;
			_model = model;
			_root = root ?? "/";
		}

		public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken) {

			var dvb = new DynamicViewBag();
			dvb.AddValue("_ApplicationRoot", _root);

			var parsedContent = RazorEngineWrapper.Parse(_template, _model, dvb);

			var response = new HttpResponseMessage(HttpStatusCode.OK) {
				Content = new StringContent(parsedContent)
			};

			response.Content.Headers.ContentType = new MediaTypeHeaderValue("text/html");

			return Task.FromResult(response);
		}
	}

	public class Template<T> : TemplateBase<T> {

		public string ApplicationRoot {
			get { return ViewBag._ApplicationRoot; }
		}

		public string Json(object obj) {
			return JsonConvert.SerializeObject(obj);
		}
	}

	/// <summary>
	/// Created as an easy to use wrapper for the razor engine, the caching is based on this article: http://stackoverflow.com/a/21330077/653458 I have cleaned it up slightly though
	/// </summary>
	internal class RazorEngineWrapper {

		static RazorEngineWrapper() {

			var templateConfig = new TemplateServiceConfiguration {
				BaseTemplateType = typeof(Template<>),
				EncodedStringFactory = new RazorEngine.Text.RawStringFactory()
			};

			RazorEngine.Razor.SetTemplateService(new TemplateService(templateConfig));
		}

		public static string Parse(string name, object model, DynamicViewBag bag = null) {

			if (RazorEngine.Razor.Resolve(name) == null) {

				RazorEngine.Razor.Compile(LoadContent(name), name);
			}

			return (bag == null) ? RazorEngine.Razor.Run(name, model) : RazorEngine.Razor.Run(name, model, bag);
		}

		private static string LoadContent(string name) {

			if (String.IsNullOrEmpty(name)) {
				throw new ArgumentException("name");
			}

			// If the template name starts with a tilde or forward slash, the template is app relative, so strip it and add the base directory
			var filename = name.StartsWith("~") || name.StartsWith("/")
								? Path.Combine(AppDomain.CurrentDomain.BaseDirectory, Regex.Replace(name, @"^(\~\/|\/)", ""))
								: name;

			var pathsToTest = new[] {
				filename + ".cshtml",
				filename + ".vbhtml",
				filename + ".html",
				filename + ".htm"
			};

			foreach (var path in pathsToTest) {

				if (File.Exists(path)) {
					return File.ReadAllText(path);
				}
			}

			throw new FileNotFoundException(filename);
		}
	}
}

namespace System.Web.Http {

	public static class ApiControllerHtmlExt {

		private const string ViewDirectory = @"/views";

		/// <summary>
		/// Returns a result to the user made up of parsed cshtml, if the view name is not supplied then it will default to finding a view of the same name as the action, in a folder the
		/// same name as the controller and under the views folder. 
		/// 
		/// If the name is supplied it should be an application root relative one. Do not include '.cshtml' as that is included automatically
		/// </summary>
		/// <returns></returns>
		public static HtmlActionResult Html(this ApiController controller) {

			var root = GetRoot(controller);
			var view = GetView(controller);

			return new HtmlActionResult(view, null, root);
		}

		/// <summary>
		/// Returns a result to the user made up of parsed cshtml, if the view name is not supplied then it will default to finding a view of the same name as the action, in a folder the
		/// same name as the controller and under the views folder. 
		/// 
		/// If the name is supplied it should be an application root relative one. Do not include '.cshtml' as that is included automatically
		/// </summary>
		/// <returns></returns>
		public static HtmlActionResult Html(this ApiController controller, string view) {

			var root = GetRoot(controller);

			return new HtmlActionResult(view, null, root);
		}

		/// <summary>
		/// Returns a result to the user made up of parsed cshtml, if the view name is not supplied then it will default to finding a view of the same name as the action, in a folder the
		/// same name as the controller and under the views folder. 
		/// 
		/// If the name is supplied it should be an application root relative one. Do not include '.cshtml' as that is included automatically
		/// </summary>
		/// <returns></returns>
		public static HtmlActionResult Html(this ApiController controller, dynamic obj) {

			var root = GetRoot(controller);
			var view = GetView(controller);

			return new HtmlActionResult(view, obj, root);
		}

		/// <summary>
		/// Returns a result to the user made up of parsed cshtml, if the view name is not supplied then it will default to finding a view of the same name as the action, in a folder the
		/// same name as the controller and under the views folder. 
		/// 
		/// If the name is supplied it should be an application root relative one. Do not include '.cshtml' as that is included automatically
		/// </summary>
		/// <returns></returns>
		public static HtmlActionResult Html(this ApiController controller, string view, dynamic obj) {

			var root = GetRoot(controller);

			return new HtmlActionResult(view, obj, root);
		}

		private static string GetRoot(ApiController controller) {

			// Gets the root by getting the absoluteUri of the application and removing the root
			return controller.Url.Content("~/").Substring(controller.Request.RequestUri.GetLeftPart(UriPartial.Authority).Length);
		}

		private static string GetView(ApiController controller) {

			return Path.Combine(ViewDirectory, controller.ControllerContext.ControllerDescriptor.ControllerName, controller.ActionContext.ActionDescriptor.ActionName);
		}
	}
}