Question

我正在制作一个有下拉列表的页面。一旦用户做出选择，客户端更改事件将根据下拉列表的选择加载Telerik网格。我当前遇到的问题是当我尝试加载页面时，出现以下错误：

对象引用未设置为对象的实例。描述：执行当前Web请求期间发生未处理的异常。请查看堆栈跟踪以获取有关错误及其源自代码的位置的更多信息。

异常详细信息：System.NullReferenceException：未将对象引用设置为对象的实例。

来源错误：

Line 30:         <tr>
Line 31:             <td colspan="2">
Line 32:                 @(Html.Telerik().Grid<ProductModel>(Model.Products.Data)
Line 33:                     .Name("classification-products-grid")
Line 34:                     .Columns(columns =>

以下是我的所有代码。如果有人有任何想法，我会很感激。感谢。

模型（ClassificationListModel.cs）

public partial class ClassificationListModel : BaseNopModel
{
    public ClassificationListModel()
    {
        Classifications = new List<ClassificationModel>();
    }

    [NopResourceDisplayName("Admin.Reports.Classifications.Classification")]
    public int Classification { get; set; }
    public List<ClassificationModel> Classifications { get; set; }

    public GridModel<ProductModel> Products { get; set; }
}

public partial class ClassificationModel : BaseNopModel
{
    public int Id { get; set; }
    public string Name { get; set; }
}

查看（Classifications.cshtml）

@model ClassificationListModel
@using Nop.Admin.Models.Reports;
@using Telerik.Web.Mvc.UI;
@{
var gridPageSize = EngineContext.Current.Resolve<Nop.Core.Domain.Common.AdminAreaSettings>().GridPageSize;
ViewBag.Title = @T("Admin.Reports.Classifications").Text;
}
@using (Html.BeginForm())
{
<div class="section-header">
    <div class="title">
        <img src="@Url.Content("~/Administration/Content/images/ico-catalog.png")" alt="" />
        @T("Admin.Reports.Classifications")
    </div>
</div>

<table width="100%">
    <tr>
        <td class="adminTitle">
            @Html.NopLabelFor(model => model.Classification)
        </td>
        <td class="adminData">
            @Html.DropDownListFor(model => model.Classification, new SelectList(Model.Classifications, "Id", "Name"), "Select a Classification")
        </td>
    </tr>
    <tr>
        <td colspan="2">
        </td>
    </tr>
    <tr>
        <td colspan="2">
            @(Html.Telerik().Grid<ProductModel>(Model.Products.Data)
                .Name("classification-products-grid")
                .Columns(columns =>
                {
                    columns.Bound(x => x.Id)
                        .ReadOnly(true)
                        .Visible(false);
                    columns.Bound(x => x.Name);
                    columns.Bound(x => x.Published)
                        .Width(100)
                        .Template(x => x.Published.ToString().ToLower())
                        .Centered();
                })
                .Pageable(settings => settings.Total(Model.Products.Total).PageSize(gridPageSize).Position(GridPagerPosition.Both))
                .ClientEvents(events => events.OnDataBinding("onDataBinding"))
                .DataBinding(dataBinding => dataBinding.Ajax().Select("ProductList", "Reports"))
                .EnableCustomBinding(true))
        </td>
    </tr>
</table>

<script type="text/javascript">
    $(document).ready(function () {
        $("#Classification").change(function () {
            $("#classification-products-grid").data("tGrid").rebind();
        });
    });

    function onDataBinding(e) {
        var specificationOptionId = $("#Classification").data("tDropDownList").value();

        if (specificationOptionId != 0)
            e.data = $.extend(e.data, {
                specificationOptionId: $("#Classification").data("tDropDownList").value()
            });
    }
</script>
}

Controller（ReportsController.cs）

[AdminAuthorize]
public class ReportsController : BaseNopController
{
    #region Fields
    private readonly IPermissionService _permissionService;
    private readonly IProductService _productService;
    private readonly ISpecificationAttributeService _specificationAttributeService;
    private readonly IWorkContext _workContext;
    #endregion

    #region Constructor
    public ReportsController(IPermissionService permissionService, IProductService productService,
        ISpecificationAttributeService specificationAttributeService, IWorkContext workContext)
    {
        this._permissionService = permissionService;
        this._productService = productService;
        this._specificationAttributeService = specificationAttributeService;
        this._workContext = workContext;
    }
    #endregion

    #region Utilities
    [NonAction]
    private List<ClassificationModel> PrepareClassificationListModel(IList<SpecificationAttributeOption> specificationAttributeOptions)
    {
        var returnData = new List<ClassificationModel>();

        foreach (var specificationAttributeOption in specificationAttributeOptions)
        {
            var classification = new ClassificationModel
            {
                Id = specificationAttributeOption.Id,
                Name = specificationAttributeOption.Name
            };
            returnData.Add(classification);
        }

        return returnData;
    }
    #endregion

    #region Methods
    #region Classifications
    public ActionResult Index()
    {
        return RedirectToAction("Classifications");
    }

    public ActionResult Classifications()
    {
        var classificationListModel = new ClassificationListModel();
        var specificationAttributeOptions = _specificationAttributeService.GetSpecificationAttributeOptionsBySpecificationAttribute(5);
        var classifications = PrepareClassificationListModel(specificationAttributeOptions);
        classificationListModel.Classifications = classifications;
        return View(classificationListModel);
    }

    [HttpPost, GridAction(EnableCustomBinding = true)]
    public ActionResult ProductList(GridCommand command, int specificationOptionId)
    {
        if (!_permissionService.Authorize(StandardPermissionProvider.ManageReports))
            return AccessDeniedView();

        if (specificationOptionId == 0)
            return View();

        var gridModel = new GridModel();
        IList<int> filterableSpecificationAttributeOptionIds = new List<int> { specificationOptionId };
        var products = _productService.SearchProducts(0, 0, null, null, null, 0, null, false,
                _workContext.WorkingLanguage.Id, null,
                ProductSortingEnum.Position, command.Page, command.PageSize,
                true, out filterableSpecificationAttributeOptionIds);

        gridModel.Data = products.Select(x =>
        {
            var productModel = x.ToModel();
            return productModel;
        });
        gridModel.Total = products.TotalCount;

        return new JsonResult
        {
            Data = gridModel
        };
    }
    #endregion
    #endregion
}

Answer 1

好的，所以我找到了答案。以下是该主题的链接：

Solution

以下是我的更改。

查看（Classifications.cshtml）

@model ClassificationListModel
@using Nop.Admin.Models.Reports;
@using Telerik.Web.Mvc.UI;
@{
var gridPageSize = EngineContext.Current.Resolve<Nop.Core.Domain.Common.AdminAreaSettings>().GridPageSize;
ViewBag.Title = @T("Admin.Reports.Classifications").Text;
}
@using (Html.BeginForm())
{
<div class="section-header">
    <div class="title">
        <img src="@Url.Content("~/Administration/Content/images/ico-catalog.png")" alt="" />
        @T("Admin.Reports.Classifications")
    </div>
</div>

<table width="100%">
    <tr>
        <td class="adminTitle">
            @Html.NopLabelFor(model => model.Classification):
        </td>
        <td class="adminData">
            @Html.DropDownListFor(model => model.Classification, new SelectList(Model.Classifications, "Id", "Name"), "Select a Classification")
        </td>
    </tr>
    <tr>
        <td colspan="2">
        </td>
    </tr>
    <tr>
        <td colspan="2">
            <div id="divGrid" style="display:none">
                @(Html.Telerik().Grid<ProductModel>(Model.Products.Data)
                    .Name("classification-products-grid")
                    .Columns(columns =>
                    {
                        columns.Bound(x => x.Id)
                            .ReadOnly(true)
                            .Visible(false);
                        columns.Bound(x => x.Name);
                        columns.Bound(x => x.Published)
                            .Width(100)
                            .Template(x => x.Published.ToString().ToLower())
                            .Centered();
                    })
                    .Pageable(settings => settings.Total(Model.Products.Total).PageSize(gridPageSize).Position(GridPagerPosition.Both))
                    .ClientEvents(events => events.OnDataBinding("onDataBinding"))
                    .DataBinding(dataBinding => dataBinding.Ajax().Select("ProductList", "Reports"))
                    .EnableCustomBinding(true))
                </div>
        </td>
    </tr>
</table>

<script type="text/javascript">
    var initialLoad = true;

    $("#Classification").change(function () {
        $("#divGrid").show();            
        $("#classification-products-grid").data("tGrid").rebind();
    });

    function onDataBinding(e) {
        if (initialLoad == true) {
            e.preventDefault();
            initialLoad = false;
        }
        else {
            var classificationId = $('#@Html.FieldIdFor(model => model.Classification)').val();
            if (classificationId != "")
                e.data = $.extend(e.data, {
                    specificationOptionId: classificationId
                });
            else {
                e.preventDefault();
                $("#divGrid").hide();
            }
        }

    }
</script>
}

根据下拉列表选择加载Telerik Grid

1 个答案: