I use SelectField in one single page directly but got error when tap select field:
Uncaught TypeError: Cannot read property 'add' of undefined

Did I missed any thing?

<%@ Page Language="C#" %>

<script runat="server">
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!X.IsAjaxRequest)
        {
        }
    }

    public void HandleSelection(object sender, DirectEventArgs e)
    {
    }
    public static readonly object SelectedEntry = new { value = "ca" };
</script>

<!DOCTYPE html>

<html>
<head runat="server">
    <title></title>
</head>
<body>
<ext:ResourceManager runat="server" />

<ext:FormPanel ID="basicform" runat="server">
    <Items>
        <ext:FieldSet
            runat="server"
            ID="fieldset1"
            Title="A"
            Instructions="">
            <Defaults>
                <ext:Parameter Name="labelWidth" Value="35%" />
            </Defaults>
            <Items>
                <ext:TextField
                    runat="server"
                    Name="name"
                    Label="Name"
                    PlaceHolder="Tom Roy"
                    AutoCapitalize="true"
                    Required="true"
                    ClearIcon="true" />
                <ext:SpinnerField
                    runat="server"
                    Name="spinner"
                    Label="Spinner"
                    MinValue="0"
                    MaxValue="10"
                    StepValue="1"
                    Cycle="true">
                </ext:SpinnerField>
                <ext:Checkbox
                    runat="server"
                    Name="cool"
                    Label="Cool" />
                <ext:SelectField
                    ID="SelectField1"
                    runat="server"
                    Label="Location"
                    AutoDataBind="true"
                    Selection="<%# SelectedEntry %>">
                    <Options>
                        <ext:ListItem Text="Brazil" Value="br" />
                        <ext:ListItem Text="Canada" Value="ca" />
                        <ext:ListItem Text="Russia" Value="ru" />
                        <ext:ListItem Text="Turkey" Value="tk" />
                    </Options>
                    <DirectEvents>
                        <Initialize OnEvent="HandleSelection">
                            <ExtraParams>
                                <ext:Parameter Name="value" Value="item.getSelection().data.value" Mode="Raw" />
                            </ExtraParams>
                        </Initialize>
                        <Change OnEvent="HandleSelection">
                            <ExtraParams>
                                <ext:Parameter Name="value" Value="newValue.data.value" Mode="Raw" />
                            </ExtraParams>
                        </Change>
                    </DirectEvents>
                </ext:SelectField>
                <ext:Slider
                    runat="server"
                    Name="slider"
                    Label="Slider" />
                <ext:ToggleField
                    runat="server"
                    Name="toggle"
                    Label="Toggle" />
                <ext:TextArea
                    runat="server"
                    Name="bio"
                    Label="Bio" />
            </Items>
        </ext:FieldSet>
    </Items>
</ext:FormPanel>
</body>
</html>