Example action filter attribute for ASP.NET WEB API

ExampleActionFilter.cs

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

namespace Server.Attributes
{
    public class ExampleFilterAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuting(HttpActionContext actionContext)
        {
            if (!actionContext.Request.Headers.Contains("Authorization"))
              throw new Exception("Token not found");
            else
            {
              var token = actionContext.Request.Headers.GetValues("Authorization").FirstOrDefault();
              User(token).Check();//Throw error if have a problem with this token
            }
            
            //Go to the next step
            base.OnActionExecuting(actionContext);
        }
    }
}