设置 Context.Response.StatusCode 似乎不起作用

我有一个带有以下代码的 HttpHandler：

using System;
using System.Web;
using Company.Cms;
using Company.Web.Handlers.Console;


namespace Company.Web.Handlers
{
    /// <summary>
    /// Summary description for AdminHandler
    /// </summary>
    public class AdminHandler : IHttpHandler
    {
        public bool IsReusable
        {
            get
            {
                return false;
            }
        }

        public void ProcessRequest(HttpContext context)
        {
            HttpRequest request = context.Request;
            HttpResponse response = context.Response;
            string action = request.QueryString["action"];

            if (!HttpContext.Current.User.CanAdminister())
            {
                response.StatusCode = 403;
                response.Status = "403 Access Denied";
                response.End();
                return;
            }

            if (String.IsNullOrEmpty(action))
            {
                response.StatusCode = 404;
                response.Status = "404 Not Found";
                response.End();
                return;
            }

            IHttpHandler handler = null;
            switch (action)
            {
                case "menu":
                    handler = new MenuHandler();
                    break;
                case "tree":
                    handler = new TreeHandler();
                    break;
                case "grid":
                    handler = new GridHandler();
                    break;
                case "list":
                    handler = new ListHandler();
                    break;
                case "drop":
                    handler = new DropHandler();
                    break;
                case "edit":
                    handler = new EditHandler();
                    break;
                case "new":
                    handler = new InsertHandler();
                    break;
            }
            if (handler == null)
            {
                response.StatusCode = 404;
                response.Status = "404 Not Found";
                response.End();
            }
            else
            {
                handler.ProcessRequest(context);
            }
        }
    }
}

不幸的是，当我故意指定无效操作时，浏览器只显示空白页面。 Firefox 和 IE 中均不会显示任何浏览器错误消息。

我可能做错了什么？

EDIT- IE 显示错误消息，但 Firefox 不显示。

首先尝试这个：

protected void Page_Load(object sender, EventArgs e)
{
    Response.StatusCode = 404;
    Response.SuppressContent = true;
    HttpContext.Current.ApplicationInstance.CompleteRequest();
}

:)~