Q:

Page not refreshing partially

I am using ASP.net 3.5 and Ajax toolkit is 2.0.  Following is my code and my page is not refreshing partially.  Is there any way to debug where is the issue? 
<form id="form1" runat="server">
    <div>
        <asp:ScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering="true">
        </asp:ScriptManager>
        <asp:DropDownList ID="ddl_country" runat="server" Style="width: 100%;" OnSelectedIndexChanged="ddl_country_SelectedIndexChanged"
            AutoPostBack="true">
        </asp:DropDownList>
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <ContentTemplate>
                <div id="div_Port_ddl" runat="server" style="width: 100%;">
                    <asp:DropDownList ID="ddl_port" runat="server" AutoPostBack="True" Width="100%" onchange="SetPortId(this);"
                        OnSelectedIndexChanged="ddl_port_SelectedIndexChanged">
                    </asp:DropDownList>
                </div>
            </ContentTemplate>
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="ddl_country" EventName="SelectedIndexChanged" />
            </Triggers>
        </asp:UpdatePanel>
    </div>
    </form>

A:

You could set the UpdateMode of your Update Panel to Conditional.   Then in the SelectIndexChanged of "ddl_Country" you could call UpdatePanel1.Update().