Custom Authorize Attribute in Web API

I want to create my custom authorization in web api controller to check the roles of the user and if its active user. So far this is my code and I don't know yet how/what to override in this codes. Thanks! your help is appreciated :D

using Avanza.Conference.Persistence;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using System.Web.Http.Controllers;

namespace Avanza.Conference.Core.Extensions
{
    public class CustomAuthorizeAttribute : AuthorizeAttribute
    {
        ApplicationDbContext _context = new ApplicationDbContext(); // my entity  

        public override void OnAuthorization(HttpActionContext actionContext)
        {

            //Sample on what to do here??
            if (AuthorizeRequest(actionContext))
            {

                return;

            }

            HandleUnauthorizedRequest(actionContext);

        }

        protected override void HandleUnauthorizedRequest(HttpActionContext actionContext)
        {

            //Code to handle unauthorized request
            var challengeMessage = new HttpResponseMessage(HttpStatusCode.Unauthorized);
            challengeMessage.Headers.Add("WWW-Authenticate", "Basic");
            throw new HttpResponseException(challengeMessage);

        }

        private bool AuthorizeRequest(HttpActionContext actionContext)
        {

            //Sample on what to do here??

            return true;

        }

    }
}