ASP.NET MVC错误：序列化对象时检测到循环引用

Question

请如何解决此错误

序列化对象时检测到循环引用 在

    public JsonResult SelectStates(int id)
{
    IEnumerable<BPP.CCSP.Admin.Web.BPPCCSPAdminStatesService.STATES> states = _statesService.GetStates().Where(stat => stat.COUNTRY_ID == id);
    return Json(states);
}

STATES定义：

public int STATE_ID { get; set; } 
public Nullable<int> COUNTRY_ID { internal get; set; } 
public string STATE_NAME { get; set; }

Answer 1

解决了。我用过这段代码

        public JsonResult GetStates(string id)
    {
        List<SelectListItem> states = new List<SelectListItem>();
        var stateList = this.Getstate(Convert.ToInt32(id));
        var stateData = stateList.Select(m => new SelectListItem()
        {
            Text = m.STATE_NAME,
            Value = m.STATE_ID.ToString(),
        });
        return Json(stateData, JsonRequestBehavior.AllowGet);
    }

由于