Bind Drop Down in Knockout

knockout-dropdown.cshtml

<section>
                                                        <label class="label">To: </label>
                                                        <label class="select">
                                                            <select class="form-control input-sm" data-bind="options: emailList,
                                                        optionsText: 'Name',
                                                        optionsValue: 'ID',
                                                        optionsCaption: '-- Select --'"></select>
                                                            <i></i>
                                                        </label>
                                                    </section>
      
// Controller                                                          
  [HttpPost]
        public async Task<JsonResult> GetTaskSourceEmails(int taskSourceId)
        {
            using (var tsEmailMgr = new TaskSourceEmailMgr())
            {
                var taskSourceEmailList = (await tsEmailMgr.GetTaskSourceEmails(taskSourceId)).Select(x => new LookUp
                {
                    ID = x.TaskSourceEmailID,
                    Name = x.TaskSourceEmail
                });

                return Json(new { taskSourceEmailList, JsonRequestBehavior.AllowGet});
            }
        }

// Business Logic
  public async Thread.Task<List<TaskSourceEmailDTO>> GetTaskSourceEmails(int taskSourceId)
        {
            var query = (from ts in m_context.TaskSourceEmails
                        
                         where ts.TaskSourceID == taskSourceId
                         select new TaskSourceEmailDTO
                         {
                             TaskSourceID = ts.TaskSourceID,
                             TaskSourceEmailID = ts.TaskSourceEmailID,
                             TaskSourceEmail = ts.TaskSourceEmail
                         }
                        );

            return await query.Distinct().ToListAsync();
        }

// Knockout - parameters in knockout must match parameters coming from Controller
// get values in mapping function
var mapData = function (data) {
  
		self.sourceId(data.detail.Task.TaskSourceId);
  
    var taskSourceId = data.detail.Task.TaskSourceId;
		$.post("/Task/GetTaskSourceEmails/", { taskSourceId: taskSourceId }, function (data) {
		    self.emailList(data.taskSourceEmailList);
		});
}

// mapping is called in Load() function
function Load(allData) {
		// Load initial state from server
		if ($.isEmptyObject(allData)) {
			$.post("/Task/GetDetail", { taskId: detailId }, function success(data, textStatus, jqXHR) {
				mapData(data);
			});
		} else {
			mapData(allData);
		}

		//Builds task history and set the timer to auto refresh
		getTaskHistory();
	}