TypeError: a在asp.net MVC中的Select2插件中是未定义的

我在另一个下拉菜单的on change事件上创建了Select，下面是我的脚本:

$ddlOther.on('change', function(e) {
        var Json = {},
            persons = [];
        Json.id = $(this).val();
        $.post('/PersonController/GetPersonDDL', Json, function(data) {
            drivers = data;
        }, 'json').done(function(data) {
            $person.select2({
                placeholder: "Select Persons(s)",
                allowClear: true,
                multiple: true,
                data:  persons
            });
        });
    });

public ActionResult GetPersonDDL(JsonDictionary args)
{
     JsonResult result = null;
     string id= args["id"].Trim();
     var persons = _context.Persons
                           .Where(x => x.id== id)
                            .Select(x => new 
                                             { x.first_name, 
                                               x.middle_name, 
                                               x.last_name, x.id
                                              }).ToList();

     foreach (var person in persons)
     {
             var item = new SelectListItem
             {
                   Text = string.Format("{0} - {1} {2} {3}", 
                                                          person.id, 
                                                          person.first_name, 
                                                          person.middle_name,
                                                          person.last_name),
                    Value = person.id
                    };
                    list.Add(item);
                }
      result = Json(list.Select(x=>new {value = x.Text, 
                                        id = x.Value}
                                ), JsonRequestBehavior.AllowGet);

      return result;
}

我得到了数据，但是控制台(在本例中是firebug)给了我错误:

TypeError: a is undefined

返回的JSON如下所示:

[ 
  Object { value="John Doe", id="1"}, 
  Object { value="Jane Doe" id="2"} 
]