javascript - ASP.Net Razor Pages - 如何将 json 从 razor 页面返回到 javascript $.getJson？

Question

我对 Web 开发非常陌生，我已经搜索了一段时间，但似乎找不到解决方案。我在 asp.net core 2.0 中使用 Razor 页面，我想根据另一个下拉框的选择填充一个下拉框。当第一个下拉框的值发生变化时，我设置了以下 javascript 以在我的 Razor 页面中点击一个过程。但是，当我运行代码时，我无法让它工作。我认为这是由于我的返回值，但我似乎无法将其设为 json 值，因为当我尝试这样做时它不断向我抛出错误。错误是“JSON 在此上下文中无效”。谁能向我建议如何将 JSON 从 Razor 页面返回到 javascript 调用？

任何帮助，将不胜感激!

    @section Scripts {
<script type="text/javascript">
    $('#Department').change(function () {
        var selectedDepartment = $("#Department").val();
        var cardSelect = $('#Card');
        cardSelect.empty();
        if (selectedDepartment != null && selectedDepartment != '') {
            $.getJSON('@Url.Action("GetCardsByDivisionAndStatus")', { divisionID: selectedDepartment }, function (cards) {
                if (cards != null && !jQuery.isEmptyObject(cards)) {
                    cardSelect.append($('<option/>', {
                        Card_ID: null,
                        Card_Number: ""

                    }))
                    $.each(cards, function (index, card) {
                        cardSelect.append($('<option/>', {
                            Card_ID: card.Card_ID,
                            Card_Number: card.Card_Number
                        }));

                    });

                };

            });                                
        }
    });
</script>

}

这是我的 C# 代码(我尝试使用 JsonResult 但这也不起作用):

           // If the user selects a division then make sure to get the cards for that division only
    [HttpGet]
    public ActionResult GetCardsByDivisionAndStatus(string divisionID)
    {
        int checkinStatus;
        int intdivisionID;

        if (divisionID != "0" && divisionID != null)
        {
            // Retrieve a status of checked in so that only cards with a checked in status can
            // be checked out.
            checkinStatus = linqQuery.GetCardStatusByStatusDesc("Checked In", _Context);

            intdivisionID = Convert.ToInt32(divisionID);

            // Retrieve list of cards that have the checkin status ID
            CardList = linqQuery.GetCardListByStatusIDandDeptID(checkinStatus, intdivisionID, _Context);

            // Create the drop down list to be used on the screen.
            carddropdown = new List<CardDropDown>();
            carddropdown = loaddropdowns.ReturnDropDownList(CardList);
            return new JsonResult(CardList);
        }

        return null;
    } 

编辑 - - - - - - - - - - - - - - - - - - - - - - - - - ----------

所以我改变了代码如下，现在我得到一个解析错误“JSON.parse:JSON数据的第1行第1列的意外字符”我无法弄清楚发生了什么，因为我看不到什么数据回来了，它无法解析。我下面的代码是否没有转换为 JSON，如果没有，我错过了什么？

    @section Scripts {
<script type="text/javascript">
    $('#Department').change(function () {
        var selectedDepartment = $("#Department").val();                 
        var cardSelect = $('#Card');
        cardSelect.empty();
        if (selectedDepartment != null && selectedDepartment != '') {
            $.getJSON('@Url.Action("/CheckOutCard?handler=CardsByDivisionAndStatus")', { divisionID: selectedDepartment }, function (cards) {
                if (cards != null && !jQuery.isEmptyObject(cards)) {
                    cardSelect.append($('<option/>', {
                        Card_ID: null,
                        Card_Number: ""

                    }))
                    $.each(cards, function (index, card) {
                        cardSelect.append($('<option/>', {
                            Card_ID: card.Card_ID,
                            Card_Number: card.Card_Number
                        }));

                    });

                };

            });                                
        }
    });
</script>

这是我更新的过程的 C# 代码:

            // If the user selects a division then make sure to get the cards for that division only
    [HttpGet]
    public JsonResult OnGetCardsByDivisionAndStatus(string divisionID)
    {
        int checkinStatus;
        int intdivisionID;

        if (divisionID != "0" && divisionID != null)
        {
            // Retrieve a status of checked in so that only cards with a checked in status can
            // be checked out.
            checkinStatus = linqQuery.GetCardStatusByStatusDesc("Checked In", _Context);

            intdivisionID = Convert.ToInt32(divisionID);

            // Retrieve list of cards that have the checkin status ID
            CardList = linqQuery.GetCardListByStatusIDandDeptID(checkinStatus, intdivisionID, _Context);

            // Create the drop down list to be used on the screen.
            carddropdown = new List<CardDropDown>();
            carddropdown = loaddropdowns.ReturnDropDownList(CardList);
            var converted = JsonConvert.SerializeObject(carddropdown);
            return new JsonResult(converted);
        }

        return null;
    }

Answer 1

将您的方法重命名为 获取 CardsByDivisionAndStatus (注意“OnGet”前缀)并在 jquery 代码中将 url 更改为

$.getJSON('/{PageRoute}?handler=CardsByDivisionAndStatus'
e.g.
$.getJSON('/About?handler=CardsByDivisionAndStatus'

请注意，处理程序查询字符串参数名称将是您的方法名称，没有 获取 字首。