title: Cannot render events FullCalendar with JSON
body: <p>I'm using FullCalendar ver 3.9.0. I have an issue. The events do not render result of JsonResult in MVC. I checked it by javascript: <code>$('#calendar').fullCalendar('clientEvents');</code> and it returns no length. But when I use <code>$.ajax</code> then it returns two arrays like this: <code>[{"id":5275,"title":"Test Image","start":"23/08/2018 16:39:47","end":"26/08/2018 16:39:47","backgroundColor":"#17a2b8"},{"id":5276,"title":"Test video","start":"23/08/2018 16:39:47","end":"26/08/2018 16:39:47","backgroundColor":"#17a2b8"}]</code></p>
  
  <p>FullCalendar's config:</p>
  
  <pre><code>$('#calendar').fullCalendar({
          defaultView: 'basicWeek',
          themeSystem: 'bootstrap4',
          editable: true,
          header: {
              left: 'prev,next today',
              center: 'title',
              right: 'month,basicWeek,basicDay,listWeek'
          },
          events: {
              url: '/Schedule/TrinhChieuSchedule',
              type: 'POST',
              data: model
          },
          success: function(data) {
              console.log(data);
          },
          error: function(err) {
              AlertMessageDefaultPosition(err, "warning");
              console.log(err);
          },
      });
  </code></pre>
  
  <p>And this is JsonResult in MVC:</p>
  
  <pre><code>public JsonResult TrinhChieuSchedule(ScheduleJsonModel model)
          {
              DateTime? ngayBatDau = null;
              DateTime? ngayKetThuc = null;
  
              if (!String.IsNullOrEmpty(model.ngayBatDau))
                  ngayBatDau = DateTime.Parse(model.ngayBatDau);
  
              if (!String.IsNullOrEmpty(model.ngayKetThuc))
                  ngayKetThuc = DateTime.Parse(model.ngayKetThuc);
  
              var list = db.SPC_SP_TrinhChieuSchedule(model.madv, ngayBatDau, ngayKetThuc);
  
              var serializer = new JavaScriptSerializer();
  
              var jsonString = serializer.Serialize(list.ToArray());
  
              return Json(jsonString);
          }
  </code></pre>