DHTMLX Scheduler with Registration Form

Question

I am trying to display events in the dhtmlx scheduler and pass the clicked event id to another registration form (view). I can get the event_id but I have no clue how to pass the event_id to controller action. My sample code is below:

        <h2>Appointment Calendar</h2>
    @using (Html.BeginForm())
    { 
        <div class="scheduler_container" style='height: 600px;'>
            @Html.Raw(Model.Render())
    
    
        </div>
     }
    <script>
        scheduler.attachEvent("onClick", function (id, e) {
        
            console.log(id);
            //call controller method
            $.ajax({
                type: "POST",
                url: "/Home/Registration",
                data: { EventId: id },
                // data: {EventId:$('#event_id').val()},
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function (response) {
                    window.location.href = "Registration/" + id;
                },        
                error: function (response) {
                    
                }
            });
            //window.location.href = "Registration/" + id;
            return true;
        });
    </script>

controller:

    public  ActionResult Registration(int? EventId)  <- the EventId is null here
            {   
                var Event = db.Appointments.Where(s => s.Id.Equals(EventId)).FirstOrDefault();
                 ...
                 return View();
            }