Drop down list in Update panel

<form id="form1" runat="server">

<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering ="true"/>

<div>

&nbsp;</div>

<asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode ="Conditional" >

<ContentTemplate>

<asp:DropDownList ID="DropDownList1" runat="server" DataTextField="fieldname" DataValueField="fieldname" autopostback="true" OnSelectedIndexChanged ="DropDownList1_SelectedIndexChanged">

</asp:DropDownList>

<asp:DropDownList ID="DropDownList2" runat="server" DataTextField="Text" DataValueField="Val">

</asp:DropDownList>

</ContentTemplate>

<Triggers >

<asp:AsyncPostBackTrigger ControlID ="DropDownList1" EventName ="SelectedIndexChanged" />

</Triggers>

</asp:UpdatePanel>

<asp:UpdatePanel ID="UpdatePanel2" runat="server" UpdateMode ="conditional" >

<ContentTemplate>

<asp:Button ID="Button1" runat="server" Text="Button" /><br />

<asp:Label ID="Label1" runat="server" Text="Label" Width="152px"></asp:Label>

</ContentTemplate>

</asp:UpdatePanel>

&nbsp;

</form>
Here's the code from my form -

<td><asp:UpdatePanel ID="updateRecipe" runat="server" UpdateMode ="Conditional" >

<ContentTemplate><asp:DropDownList ID="JobDescription" runat="server" DataTextField="Text" DataValueField="val" Width="150px" CssClass ="grdData" AutoPostBack="True" OnSelectedIndexChanged ="JobDescription_SelectedIndexChanged">

</asp:DropDownList> </ContentTemplate><Triggers >

<asp:AsyncPostBackTrigger ControlID ="JobDescription" EventName ="SelectedIndexChanged" />

</Triggers></asp:UpdatePanel>