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我很难弄清楚如何让级联下拉列表适用于我的 asp.net mvc3 应用程序。我有一个弹出框,我想显示 2 个下拉列表,第二个是根据第一个中选择的内容填充的。每次我运行应用程序时,控制器方法都会返回正确的值列表,但我没有点击 ajax 调用的成功部分,而是点击了错误部分。我做了很多研究并遵循了几个我发现的例子,但有些地方仍然不太正确,任何帮助将不胜感激。

编辑:使用 firebug 进一步检查显示错误 500 内部服务器错误,其中指出:异常详细信息:System.InvalidOperationException:在序列化“System.Data.Entity.DynamicProxies.GameEdition”类型的对象时检测到循环引用

我有以下 jQuery / AJAX:

<script type="text/javascript">
$(function () {
    $("#PlatformDropDownList").change(function () {
        var gameId = '@Model.GameID';
        var platformId = $(this).val();
        // and send it as AJAX request to the newly created action 
        $.ajax({
            url: '@Url.Action("Editions")',
            type: 'GET',
            data: { gameId: gameId, platformId: platformId },
            cache: 'false',
            success: function (result) {
                $('#EditionDropDownList').empty();
                // when the AJAX succeeds refresh the ddl container with 
                // the partial HTML returned by the PopulatePurchaseGameLists controller action 
                $.each(result, function (result) {
                    $('#EditionDropDownList').append(
                        $('<option/>')
                            .attr('value', this.EditionID)
                            .text(this.EditionName)
                    );

                });
            },
            error: function (result) {
                alert('An Error has occurred');
            }
        });
    });
});

这是我的控制器方法:

  public JsonResult Editions(Guid platformId, Guid gameId)
  {
     //IEnumerable<GameEdition> editions = GameQuery.GetGameEditionsByGameAndGamePlatform(gameId, platformId);
     var editions = ugdb.Games.Find(gameId).GameEditions.Where(e => e.PlatformID == platformId).ToArray<GameEdition>();

     return Json(editions, JsonRequestBehavior.AllowGet);
  }

这是我的网络表单html:

<div id="PurchaseGame">
@using (Html.BeginForm())
{
    @Html.ValidationSummary(true, "Please correct the errors and try again.")
    <div>
        <fieldset>
            <legend></legend>
            <p>Select the platform you would like to purchase the game for and the version of the game you would like to purchase.</p>

            <div class="editor-label">
                @Html.LabelFor(model => model.PlatformID, "Game Platform")
            </div>
            <div class="editor-field">
                @Html.DropDownListFor(model => model.PlatformID, new SelectList(Model.Platforms, "GamePlatformID", "GamePlatformName"), new { id = "PlatformDropDownList", name="PlatformDropDownList" })
            </div>

            <div class="editor-label">
                @Html.LabelFor(model => model.EditionID, "Game Edition")
            </div>
            <div id="EditionDropDownListContainer">
                @Html.DropDownListFor(model => model.EditionID, new SelectList(Model.Editions, "EditionID", "EditionName"), new { id = "EditionDropDownList", name = "EditionDropDownList" })
            </div>

            @Html.HiddenFor(model => model.GameID)
            @Html.HiddenFor(model => model.Platforms)

            <p>
                <input type="submit" name="submitButton" value="Purchase Game" />
                <input type="submit" name="submitButton" value="Cancel" />
            </p>

        </fieldset>
    </div>
}

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1 回答 1

4

您不能使用 GET 动词发送 JSON 编码请求。所以替换type: 'GET'type: 'POST'它会起作用。此外,由于您指定了 JSON 请求,您必须发送一个 JSON 请求,该请求通过以下JSON.stringify函数实现:data: JSON.stringify({ gameId: gameId, platformId: platformId }),. 但由于您只有 2 个值,我认为使用 GET 会更容易。所以我的建议是删除contentType: 'application/json'参数并让您的 AJAX 请求如下所示:

$.ajax({
    url: '@Url.Action("Editions")',
    type: 'GET',
    data: { gameId: gameId, platformId: platformId },
    cache: 'false',
    success: function (result) {
        $('#EditionDropDownList').empty();
        // when the AJAX succeeds refresh the ddl container with 
        // the partial HTML returned by the PopulatePurchaseGameLists controller action 
        if(result.length > 0)
        {
            $.each(result, function (result) {
                $('#EditionDropDownList').append(
                    $('<option/>')
                         .attr('value', this.EditionID)
                         .text(this.EditionName)
                );
            });
        }
        else
        {
            $('#EditionDropDownList').append(
                $('<option/>')
                    .attr('value', "")
                    .text("No edition found for this game")
            );
        }

    },
    error: function () {
        alert('An Error has occured');
    }
});

同样在DropDownListForRazor 标记的助手中,我注意到以下内容:

onchange = "Model.PlatformID = this.value;"

我只能说,这并没有像你想象的那样做。


更新:

您似乎收到了循环对象引用错误,因为您将editions域模型传递给 Json 方法。循环引用对象层次结构不能被 JSON 序列化。此外,您不需要通过将包含在此版本中的所有废话发送给客户端来浪费带宽。您的所有客户需要的是一组 id 和名称。所以只需使用视图模型:

public ActionResult Editions(Guid platformId, Guid gameId)
{
    var editions = ugdb
        .Games
        .Find(gameId)
        .GameEditions
        .Where(e => e.PlatformID == platformId)
        .ToArray<GameEdition>()
        .Select(x => new 
        {
            EditionID = x.EditionID,
            EditionName = x.EditionName
        })
        .ToArray();

    return Json(editions, JsonRequestBehavior.AllowGet);
}
于 2012-06-19T06:03:50.840 回答