ASP WebAPi better ApiController NotFound method with negociated response content

ApiController.cs

namespace MyWebApi
{
    public abstract class ApiController : System.Web.Http.ApiController
    {
        /// <summary>
        /// Returns a NotFound HTTP result (404) with a negotiated full-bodyed result.
        /// </summary>
        /// <returns></returns>
        protected override System.Web.Http.Results.NotFoundResult NotFound()
        {
            var result = new MyWebApi.NotFoundResult(this); // this inherits from System.Web.Http.Results.NotFoundResult
            var error = new HttpError("Not found");
            error.Add("HttpCode", 404);
            error.Add("ErrorCode", "NotFound");
            error.Add("ErrorDetail", "No such entity. ");
            error.Add("ErrorMessage", "No such entity. ");
            error.Add("Succeed", false);
            result.Error = error;
            return result;
        }

        /// <summary>
        /// Returns a NotFound HTTP result (404) with a negotiated full-bodyed result.
        /// </summary>
        /// <returns></returns>
        protected System.Web.Http.Results.NotFoundResult NotFound(string message)
        {
            var result = new MyWebApi.NotFoundResult(this); // this inherits from System.Web.Http.Results.NotFoundResult
            var error = new HttpError("Not found");
            error.Add("HttpCode", 404);
            error.Add("ErrorCode", "NotFound");
            error.Add("ErrorDetail", message ?? "No such entity. ");
            error.Add("ErrorMessage", message ?? "No such entity. ");
            error.Add("Succeed", false);
            result.Error = error;
            return result;
        }

        /// <summary>
        /// Returns a forbidden HTTP result (403) with a negotiated full-bodyed result.
        /// </summary>
        /// <returns></returns>
        protected IHttpActionResult Forbidden()
        {
            var error = new HttpError("Forbidden");
            error.Add("HttpCode", 403);
            error.Add("ErrorCode", "Forbidden");
            error.Add("ErrorDetail", "Access denied. ");
            error.Add("ErrorMessage", "Access denied. ");
            error.Add("Succeed", false);
            var result = new NegotiatedContentResult<HttpError>(HttpStatusCode.Forbidden, error, this);
            return result;
        }
    }
}

NotFoundResult.cs

namespace MyWebApi
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Net;
    using System.Net.Http;
    using System.Threading;
    using System.Threading.Tasks;
    using System.Web.Http;
    using System.Web.Http.Results;

    /// <summary>
    /// Custom implementation of the NotFoundResult that returns a negociated content.
    /// </summary>
    public class NotFoundResult : System.Web.Http.Results.NotFoundResult
    {
        private readonly ApiController controller;

        public NotFoundResult(HttpRequestMessage request)
            : base(request)
        {
        }

        public NotFoundResult(ApiController ctrl)
            : base(ctrl)
        {
            this.controller = ctrl;
        }

        public HttpError Error { get; set; }

        public override Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
        {
            var message = this.Request.CreateResponse(HttpStatusCode.NotFound);

            if (this.Error == null)
            {
                this.Error = new HttpError();
                this.Error.Add("HttpCode", 404);
                this.Error.Add("ErrorCode", "NotFound");
                this.Error.Add("ErrorDetail", "No such entity. ");
                this.Error.Add("ErrorMessage", "No such entity. ");
                this.Error.Add("Succeed", false);
            }

            var negociator = new NegotiatedContentResult<HttpError>(HttpStatusCode.NotFound, this.Error, this.controller);
            return negociator.ExecuteAsync(cancellationToken);
        }
    }
}