如何处理objectcontext实例已经被处理掉了

Question

[HttpPost]
    public ActionResult Charter(List<int> stateIds)
    {
        try
        {
            if (!stateIds.Any())
            {
                return Json("State list is empty", JsonRequestBehavior.AllowGet);
            }

            var states = new List<CfVersionEntities.Model.State>();
            stateIds.ForEach(id =>
            {
                using (var db = new Storage_cfEntities())
                {

                        var stateList = db.States.Where(i => i.Id == id).ToList();//get names of states with matching id and save in array named
                    if (!stateList.Any()) return;
                    var state = stateList[0];
                    states.Add(state);
                }
          });
            return !states.Any() ? Json(new List<State>(), JsonRequestBehavior.AllowGet) : Json(states, JsonRequestBehavior.AllowGet);
        }
        catch (Exception)
        {
            return Json(new List<State>(),
                JsonRequestBehavior.AllowGet);
        }
    }

我有一个方法接受来自我的jquery脚本的值，如下所示，脚本工作正常并发送值，值在我的方法中接收，我已经确认。但是当我运行它时，我得到错误：ObjectContext实例已被处理，不能再用于需要连接的操作....我使用来自我的jquery的值来遍历我的数据库并选择具有的行相应的ID，我然后将此结果发送回我的jquery中的另一个函数，该函数创建一个带有值的高图

这是我的视图，其中包含我的脚本。     

国家名单

<p>
    <h2> @Html.ActionLink("Add A New State", "CreateState")</h2>
</p>
<table class="table">
    <tr>
        <th>
            @Html.DisplayNameFor(model => model.Name)
        </th>
        <th>
            @Html.DisplayNameFor(model => model.Stations)
        </th>
        <th></th>
    </tr>
    @foreach (var item in Model)
    {
        <tr>
            <td>
                @Html.DisplayFor(modelItem => item.Name)
            </td>
            <td>
                @Html.DisplayFor(modelItem => item.Stations)
            </td>
            <td>
                @Html.ActionLink("Update Stations", "UpdateStation", new {id = item.Id})||
                <div>
                    <input type="checkbox" id="@item.Id" value="@item.Id" class="chk" onclick="setChecked(this)"> <label >Add to Chart</label>
                </div>
            </td>
        </tr>
    }
</table>
<div id="charts" style="width:100%" height="400px;"></div>



<input type="button" value="Verify Selections" onclick="submit()"/>
<input type="button" value ="View Chart" onclick="location.href='@Url.Action("Charter")'" />

<script type="text/javascript">
    var collection = [];
    function setChecked(el) {

        var id = $(el).attr('id');
        if ($(el).is(':checked')) 
        {
            collection.push(id);
        } else {
            $.each(collection, function (item, index)
            {
                if (item === id)
                {
                    collection.splice(index, 1);
                }
            });
        }

    }

    function submit() {
        if (collection == null || collection.length < 1) {
            alert('please select at least one state.');
            return;
        }

        $.ajax({
            type: "POST",
            url: '/State/Charter',
            data: { stateIds: collection },
            dataType: 'application/json',
            success: function (response)
            {
                if (response.length > 0) {

                    designChart(response);
                }
            }

        });
    }

    function designChart(response)
    {
        var names = [];
        var stations = [];

        $.each(response, function (item) {
            if (item.Id > 0) {
                names.push(item.Name);
                stations.push(item.Stations);
            }
        });

        $("#charts").highcharts({
            chart:
            {
                type: 'line'
            },
            title: {
                text: 'States'
            },
            xAxis: {
                categories: names
            },
            yAxis:
                {
                    title:
                        {
                            text: 'Stations',
                            categories: stations
                        }
                }
        });
    }
</script>