Access to HttpContext User Name in call back handler

You can access the controller using Controller property in the backend class:

public class SchedulerController : Controller
{

  public ActionResult Backend()
  {
      return new Dps().CallBack(this);
  }

  class Dps : DayPilotScheduler
  {

      protected override void OnInit(InitArgs ea)
      {
      
        var c = Controller;

        // ...