Hello,

I am trying to render a form with a combobox from server-side but I am running into a javascript error when I try to re-render the form:

JavaScript runtime error: Unable to get property 'on' of undefined or null reference
and it appears to be coming from the following code:

bindStoreListeners:function(a){var c=this,b=Ext.apply({},c.getStoreListeners(a));if(!b.scope){b.scope=c}c.storeListeners=b;a.on(b)}
Sample code is as follows:


        private object[] Data
        {
            get
            {
                return new object[]
                {
                    new object[] { "TEST1", "TEST1" },
                    new object[] { "TEST2", "TEST2" },
                    new object[] { "TEST3", "TEST3" }
                };
            }
        }

        protected void Page_Load(object sender, EventArgs e)
        {
            StoreCountries.DataSource = Data;
            StoreCountries.DataBind();

            Generate_Fields();
        }

        [DirectMethod]
        public void Generate_Fields()
        {
            FormPanel aFormPanel = new FormPanel();
            aFormPanel.ID = "frmFields";

            ComboBox aComboBox = new Ext.Net.ComboBox();
            aComboBox.ID = "cmbTest";
            aComboBox.FieldLabel = "TEST";
            aComboBox.ValueField = "CODE";
            aComboBox.DisplayField = "DESCRIPTION";
            aComboBox.StoreID = "StoreCountries";
            aFormPanel.Items.Add(aComboBox);

            aFormPanel.Render(frmFields, RenderMode.Replace, true);
        }
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="com.bspr.crbspr.pages.WebForm1" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">

    <ext:ResourceManager ID="rsmMain" runat="server" Theme="Gray">
    </ext:ResourceManager>

    <ext:Store ID="StoreCountries" runat="server">
        <Model>
            <ext:Model ID="Model6" Runat="Server">
                <Fields>
                    <ext:ModelField Name="CODE" />
                    <ext:ModelField Name="DESCRIPTION" />
                </Fields>
            </ext:Model>
        </Model>
    </ext:Store>

    <ext:Viewport ID="vwpMain" runat="server" border="false" Layout="FitLayout">
        <Items>

            <ext:Panel runat="server">
                <Items>
                    <ext:FormPanel ID="frmFields" runat="server" Header="false" Border="false">
                        <Items>
                        </Items>
                    </ext:FormPanel>
                </Items>
                <Buttons>
                    <ext:Button ID="Button1" runat="server">
                        <Listeners>
                            <Click Handler="App.direct.Generate_Fields();"></Click>
                        </Listeners>
                    </ext:Button>
                </Buttons>
            </ext:Panel>

        </Items>
    </ext:Viewport>

    </form>
</body>
</html>