关于 jQuery Easyui的DataGrid使用的一个问题

页面中报错, jquery.js 中有一处报了length未定义，求指教

            $('#tb_helps').datagrid({
                url: '/Admin/PluginHelps/HotList', 
                title: '帮助内容列表',
                iconCls: 'icon-view',
                dataType:'json',
                height: 650,
                width: function () { return document.body.clientWidth * 0.9; },
                nowrap: true,
                autoRowHeight: false,
                striped: true,
                collapsible: true,
                pagination: true,
                pageSize: 100,
                pageList: [50, 100, 200],
                rownumbers: true,
                sortOrder: 'asc',
                remoteSort: false,
                idField: 'ID',
                columns: [[
                {
                    field: "Title",
                    title: "@T("Admin.ContentManagement.Helps.Help.Fields.Title")",
                    width: 300
                }, {
                    field: "DisplayOrder",
                    title: "@T("Admin.ContentManagement.Helps.Help.Fields.DisplayOrder")",
                    width: 150,
                }, {
                    field: "Detail",
                    title: "@T("Admin.ContentManagement.Helps.Help.Fields.Detail")",
                    width: 800,
                }, {
                    field: "Id",
                    title: "@T("Admin.Common.Edit")",
                    width: 125,
                    template: '<a href="HelpEdit/#=Id#">@T("Admin.Common.Edit")</a>'
                }
                ]]
            });

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请检查返回的json数据是不是一个数组

             $('#tb_helps').datagrid({
                //url: '/data/test.json',
                data:[
                    {
                        'Title':'Title',
                        'DisplayOrder':'DisplayOrder',
                        'Detail':'Detail',
                        'ID':"1",
                    }
                ]
                ,
                title: '帮助内容列表',
                iconCls: 'icon-view',
                dataType:'json',
                height: 650,
                width: function () { return document.body.clientWidth * 0.9; },
                nowrap: true,
                autoRowHeight: false,
                striped: true,
                collapsible: true,
                pagination: true,
                pageSize: 100,
                pageList: [50, 100, 200],
                rownumbers: true,
                sortOrder: 'asc',
                remoteSort: false,
                idField: 'ID',
                columns: [[
                {
                    field: "Title",
                    title: "Title",
                    width: 300
                }, {
                    field: "DisplayOrder",
                    title: "DisplayOrder",
                    width: 150,
                }, {
                    field: "Detail",
                    title: "Detail",
                    width: 800,
                }, {
                    field: "Id",
                    title: "Id",
                    width: 125,
                    template: '<a href="HelpEdit/#=Id#">@T("Admin.Common.Edit")</a>'
                }
                ]]
            });