Obtener datos de SQL para llenar fullcalendar

Eventos.cs

public class cEventos
    {
        private static string con;

        public cEventos()
        {
            con = ConfigurationManager.ConnectionStrings["CRMCapa"].ConnectionString;
        }

        internal List<CalendarEvent> ObtenerCalendario(DateTime inicio, DateTime final)
        {
            try
            {
                List<CalendarEvent> events = new List<CalendarEvent>();
                SqlConnection conexion = new SqlConnection(con);
                string sql = @"SELECT e.id, c.Nombre as curso, s.Nombre as sede, e.inicio, e.final FROM Eventos e
                           LEFT JOIN Cursos c ON c.id = e.idCurso
                           LEFT JOIN Sedes s ON s.id = e.idSede
                           WHERE e.inicio>=@inicio AND e.final<=@final";
                SqlCommand cmd = new SqlCommand(sql, conexion);
                cmd.Parameters.AddWithValue("@inicio", inicio);
                cmd.Parameters.AddWithValue("@final", final);

                using (conexion)
                {
                    conexion.Open();
                    SqlDataReader reader = cmd.ExecuteReader();
                    while (reader.Read())
                    {
                        events.Add(new CalendarEvent()
                        {
                            id = Convert.ToInt32(reader["id"]),
                            title = Convert.ToString(reader["curso"]),
                            description = Convert.ToString(reader["sede"]),
                            start = Convert.ToDateTime(reader["inicio"]),
                            end = Convert.ToDateTime(reader["final"]),
                        });
                    }
                }
                return events;
            }
            catch (Exception)
            {
                throw;
            }
        }
    }


    public class CalendarEvent
    {
        public int id { get; set; }
        public string title { get; set; }
        public string description { get; set; }
        public DateTime start { get; set; }
        public DateTime end { get; set; }
        public bool allDay { get; set; }
    }

    public class ImproperCalendarEvent
    {
        public int id { get; set; }
        public string title { get; set; }
        public string description { get; set; }
        public string start { get; set; }
        public string end { get; set; }
        public bool allDay { get; set; }
    }

Handler.ashx

public class JsonHandler : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/plain";
            DateTime inicio = Convert.ToDateTime(context.Request.QueryString["start"]);
            DateTime final = Convert.ToDateTime(context.Request.QueryString["end"]);

            List<int> idList = new List<int>();
            List<ImproperCalendarEvent> listaEventos = new List<ImproperCalendarEvent>();

            cEventos bd = new cEventos();

            foreach (CalendarEvent evento in bd.ObtenerCalendario(inicio, final))
            {
                listaEventos.Add(new ImproperCalendarEvent
                {
                    id = evento.id,
                    title = evento.title,
                    start = String.Format("{0:s}", evento.start),
                    end = String.Format("{0:s}", evento.end),

                    description = evento.description,                    
                });               
            }

            System.Web.Script.Serialization.JavaScriptSerializer oSerializer = new System.Web.Script.Serialization.JavaScriptSerializer();
            string sJSON = oSerializer.Serialize(listaEventos);

            context.Response.Write(sJSON);
        }

        public bool IsReusable
        {
            get { return false; }
        }
    }