jQuery Grid Plugin - jqGrid

Hi, I use jqgrid with asp.net mvc. There is a problem when I working with treegrid in adjacency model.Jquery version is 1.4.2 jquery UI is 1.8.2 and jqGrid version is 1.7.2

My script is like this:

 $(function(){

        jQuery("#treegrid").jqGrid({

            treeGrid: true,

            treeGridModel: 'adjacency',

            ExpandColumn: 'name',

            url: '/Test/TestTreeGrid/GetTreeData',

            datatype: "json",

            mtype: "POST",

            colNames: ["id", "Account" ],

            colModel: [

             { name: 'id', index: 'id', width: 1, hidden: true, key: true },

             { name: 'name', index: 'name', width: 180 }

            ],

            height: 'auto',

            pager: "#ptreegrid",

            caption: "Treegrid example"

        });})


And when first load the root data ,the server code is like this :

var jsonData = new {

                        total = 1, 

                        page = 1,

                        records = 1, 

                        rows = new[] {new {id=1,cell= new[] {"1","cash", "0", "Null", "false", "false" } }}

                    };

                    JsonResult jsresult= Json(jsonData,JsonRequestBehavior.AllowGet);

                    return jsresult;

but I got a error "a.rows is undefined" jquery.jqGrid.js (line 52 ).

Any help will be appreciated