RadComboBox Multiple Select (with checkboxes) databinding problem

[SilverLight]

hi dear telerik admin,
please see this thread : 
RadComboBox Advanced Multiple Selection

and this is my RadComboBox :

<telerik:RadComboBox ID="radcbFrom" runat="server" DataSourceID="sdsFrom_WebSites"
    DataTextField="From_WebSite" DataValueField="From_WebSite" EnableEmbeddedSkins="false"
    Skin="BlackByMe" ValidationGroup="A" Width="240px" LoadingMessage="Loading ..."
    CausesValidation="False" MaxHeight="150px" AppendDataBoundItems="True" HighlightTemplatedItems="true"
    OnClientDropDownOpening="OnClientDropDownOpening" OnClientDropDownClosing="OnClientDropDownClosing"
    OnClientSelectedIndexChanging="OnClientSelectedIndexChanging" OnClientBlur="OnClientBlur">
    <Items>
        <telerik:RadComboBoxItem runat="server" Text="All" Value="-1" />
    </Items>
    <ItemTemplate>
        <asp:CheckBox runat="server" ID="CheckBox" onclick="checkboxClick();" Text='<%# DataBinder.Eval(Container, "Text") %>' />
    </ItemTemplate>
</telerik:RadComboBox>

all of my server and client side codes are like that example.
my problem is when my page is loaded there is no "All" text next it's check box. 
what is the problem and how can i fix? 
as you see my radcombobox is a little different from that example.
in my situation there is sql datasource and AppendDataBoundItems="True"

thanks in advance

[Ivana]

Hi Silver,

As of Q2 2011, RadComboBox introduces a built-in CheckBox support. Using this functionality you will be able to define items in the markup and append the ones from the database to them. This way you don't have to deal with the text in the input area as this is all taken care of by the CheckBox functionality.

Here is an example:

<telerik:RadComboBox ID="RadComboBox1" runat="server" DataSourceID="SqlDataSource1"

    DataTextField="Name" DataValueField="ID"

    MaxHeight="150px" AppendDataBoundItems="true"

    CheckBoxes="true">

    <Items>

        <telerik:RadComboBoxItem Text="All" />

    </Items>

</telerik:RadComboBox>


<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:TelerikConnectionString %>"

    SelectCommand="SELECT [ID], [CountryID], [Name] FROM [Cities]"></asp:SqlDataSource>

I hope this will help.

All the best,
Ivana
the Telerik team