Global authentication attribute for MVC

GordibuteAttribute.cs

using System;
using System.Net;
using System.Net.Http;
using System.Web;
using System.Web.Http.Controllers;
using System.Web.Http.Filters;

namespace Gordafarid.Controllers
{
    internal class GordibuteAttribute : ActionFilterAttribute, IActionFilter
    {
        public override void OnActionExecuting(HttpActionContext actionContext)
        {
            bool CanAccess = false;
            try
            {
                // if (filterContext.HttpContext.Session["Username"] != null)
                // string Username = actionContext.ActionArguments["Username"].ToString();

                var queryStringCollection = HttpUtility.ParseQueryString(actionContext.Request.RequestUri.Query);
                string Username = queryStringCollection["Username"];

                CanAccess = true;
            }
            catch
            {
                CanAccess = false;
            }
            if (!CanAccess)
                actionContext.Response = new HttpResponseMessage(HttpStatusCode.Unauthorized);
        }
    }