[c#] Why is HttpContext.Current null?

I have a value that I use in all the application; I set this in application_start

  void Application_Start(object sender, EventArgs e)
  {
    Dictionary<int, IList<string>> Panels = new Dictionary<int, IList<string>>();
    List<clsPanelSetting> setting = clsPanelSettingFactory.GetAll();
    foreach (clsPanelSetting panel in setting)
    {
        Panels.Add(panel.AdminId, new List<string>() { panel.Phone,panel.UserName,panel.Password});
    }
    Application["Setting"] = Panels;

    SmsSchedule we = new SmsSchedule();
    we.Run();

  }

and in SmsSchedule

public class SmsSchedule : ISchedule
{
    public void Run()
    {           
        DateTimeOffset startTime = DateBuilder.FutureDate(2, IntervalUnit.Second);
        IJobDetail job = JobBuilder.Create<SmsJob>()
            .WithIdentity("job1")
            .Build();

        ITrigger trigger = TriggerBuilder.Create()
             .WithIdentity("trigger1")
             .StartAt(startTime)
             .WithSimpleSchedule(x => x.WithIntervalInSeconds(60).RepeatForever())
             .Build();

        ISchedulerFactory sf = new StdSchedulerFactory();
        IScheduler sc = sf.GetScheduler();
        sc.ScheduleJob(job, trigger);

        sc.Start();
    }
}

I want to get this value in a class.(smsjob)

   public class SmsJob : IJob 
   {  
      public virtual void Execute(IJobExecutionContext context)
      {
          HttpContext.Current.Application["Setting"]; 
      }
   }

but my problem is : HttpContext.Current is null, why is HttpContext.Current null?

Edit: When i use this code in another class of a page it works, but in this class I get the error.

In IIS7 with integrated mode, Current is not available in Application_Start. There is a similar thread here.

try to implement Application_AuthenticateRequest instead of Application_Start.

this method has an instance for HttpContext.Current, unlike Application_Start (which fires very soon in app lifecycle, soon enough to not hold a HttpContext.Current object yet).

hope that helps.