Tree View Using dynatree

Question

Hai I am facing this little problem in using dynatree with ajax call in MVC, as the tree is not showing up its just showing null,null,null as tree

My Method (json) in Controller

[HttpGet]
    public JsonResult Catalog(string filter) {

        var query = ReaderManager.Instance.GetCatalog(true, null);
        var tree = TreeService.GetNavigationTreeModel(query, c => c.Name, c => c.PublishedCount, c => c.Id);
        return Json(tree, JsonRequestBehavior.AllowGet);



    }

and my Dynatree

$("#res_catBar").dynatree({
        initAjax: {

            url: '@Url.Action("Catalog")',
            dataType: "json",
            },
            onActivate: function (node) {
            alert("rf");
            $('#responseMessage').text(node.data);
        }

    })