Kendo MVC Grid / Details Grid - child grid's controller not getting called

Does Id have to be an integer or it can be string?
It seems like in my case #=INVOICE# is getting value but it Read method to controller not sure why not getting called.

I tried looking at this example: http://demos.telerik.com/kendo-ui/grid/detailtemplate

    code:
    @(Html.Kendo().Grid<OpenInvoicesInfo>()
                  .Name("grid")
      .Columns(columns =>
      {
          columns.Bound(p => p.INVOICE).ClientTemplate("<input type='checkbox' value='#= INVOICE #' class='testclass' />").Width(4);
          columns.Bound(i => i.INVOICE).Width(15);
          ...     
      })
          .ClientDetailTemplateId("OrdersTemplate")
      .DataSource(dataSource => dataSource
          .Ajax()
          .PageSize(8)
          .Read(read => read.Action("GetOpenInvoices", "Maint", new { cust = Request.QueryString["cust"] }))
      )

    )

    <script id="OrdersTemplate" type="text/kendo-tmpl">
    @(Html.Kendo().Grid<CustomerComments>()
                                .Name("grid_#=INVOICE#")
                .Columns(columns =>
                {
                    columns.Bound(o => o.INVOICE).Width(15);
                    columns.Bound(o => o.Comment).Width(40);
                })
                .DataSource(dataSource => dataSource
                    .Ajax()
                    .PageSize(10)
                    .Read(read => read.Action("GetCustomerComments", "Maint", new { invoices = "#=INVOICE#" }))
                )
                .Pageable()
                .Sortable()
                .ToClientTemplate()
    )
</script>
          
        Controller:
        public ActionResult GetCustomerComments([DataSourceRequest] DataSourceRequest request, string invoices)
        {

            List<JNI.Enterprise.Contracts.CustomerComments> customer = InvoiceService.GetCustomerComments(invoices);

            return Json(customer.ToDataSourceResult(request));
        }

I will really appreciate if someone can reply.
Does it only work if it is in entity framework.
I am calling GetCustomerComments from a stored procedure.
It is loading the first grid fine but not calling details grid's controller method.