dropdown cascade update

[jlbantang]

hi team, how can i update another dropdownlist without posting back. i've seen the sample somewhere but its not doing anything.

html

<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
        <ContentTemplate>
            <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="false" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
                <asp:ListItem Value="0">----Select----</asp:ListItem>
                <asp:ListItem Value="101">General Admin</asp:ListItem>
                <asp:ListItem Value="102">Admin Assistant</asp:ListItem>
                <asp:ListItem Value="103">Software</asp:ListItem>
                <asp:ListItem Value="104">Recruiting</asp:ListItem>
            </asp:DropDownList>
            <asp:DropDownList ID="DropDownList2" runat="server">
                <asp:ListItem Value="0">----Select----</asp:ListItem>
                <asp:ListItem></asp:ListItem>
            </asp:DropDownList>
        </ContentTemplate>
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="DropDownList1" EventName="SelectedIndexChanged" />
        </Triggers>
    </asp:UpdatePanel>

VB

    Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles DropDownList1.SelectedIndexChanged
        DropDownList2.Items.Clear()
        Select Case DropDownList1.SelectedValue
            Case 101

                DropDownList2.Items.Add("monster truck")
                DropDownList2.Items.Add("pacman")
            Case 102
                DropDownList2.Items.Add("ghos in the shell")
                DropDownList2.Items.Add("bomber man")
        End Select
    End Sub