ComboBox inside FormPanel

[rsaldanhabr]

Hi folks, i´m having some problems when binding a combobox inside a form panel.

1 - Combobox in FormPanel

When i bind an entity to the FormPanel how do i notify the combobox to load the "sub" entity that is linked to the TipoDeLogradouroID.

<%--LOGRADOURO--%>
    <ext:Store ID="_strLogradouro" runat="server" OnRefreshData="CarregarEntidade">
        <DirectEventConfig ViewStateMode="Enabled" />
        <AutoLoadParams>
            <ext:Parameter Name="start" Value="={0}" />
        </AutoLoadParams>
        <Proxy>
            <ext:PageProxy />
        </Proxy>
        <Reader>
            <ext:JsonReader IDProperty="ID">
                <Fields>
                    <ext:RecordField Name="ID" Mapping="ID" />
                    <ext:RecordField Name="Nome" Mapping="Nome" />
                    <ext:RecordField Name="TipoDeLogradouroID" Mapping="TipoDeLogradouroID" />
                </Fields>
            </ext:JsonReader>
        </Reader>
        <Listeners>
            <DataChanged Fn="myValidateRecord" />
        </Listeners>
    </ext:Store>
    <%--VIEWPORT--%>
    <ext:Viewport ID="_vwpCorpoAtualizacao" runat="server">
        <Items>
            <ext:FormPanel ID="_fpnlLogradouro" IDMode="Static" Border="false" runat="server">
                <Items>
                    <%--TIPO DE LOGRADOURO--%>
                    <ext:ComboBox ID="_cbTipoDeLogradouro" DataIndex="TipoDeLogradouroID" IDMode="Static" runat="server" ViewStateMode="Enabled"
                        ForceSelection="true" FieldLabel="Tipo de Logradouro"
                        DisplayField="Nome" ValueField="ID" TypeAhead="false" LoadingText="Pesquisando Tipos de Logradouro..."
                        ItemSelector="tr.list-item" TriggerAction="Query" MinChars="1" AllowBlank="false"
                        BlankText="Informe o tipo">
                        <Store>
                            <ext:Store ID="_strTipoDeLogradouro" runat="server" AutoLoad="false" OnRefreshData="_strTipoDeLogradouro_RefreshData">
                                <Proxy>
                                    <ext:PageProxy />
                                </Proxy>
                                <Reader>
                                    <ext:JsonReader IDProperty="ID">
                                        <Fields>
                                            <ext:RecordField Name="ID" />
                                            <ext:RecordField Name="Nome" />
                                        </Fields>
                                    </ext:JsonReader>
                                </Reader>
                            </ext:Store>
                        </Store>
                    </ext:ComboBox>
                </Items>
            </ext:FormPanel>
        </Items>
    </ext:Viewport>

[rsaldanhabr]

how do i set the SelectIndex of a combobox that is bound to a Store that has a PageProxy (It always throws exception)