visual studio doesn't see the dropdownlist for trigger
<p>I have a VB.NET / ASP.NET web application. I added a dropdownlist into FooterTemplate of a Gridview. And I used ajax for postbacks. But when I add the dropdown to the triggers, vs gives me that error :</p>

<blockquote>
  <p>A control with ID 'DropDownList2' could not be found for the trigger in UpdatePanel 'UpdatePanel1'.</p>
</blockquote>

<p>ASP.NET code is like that :</p>

<pre><code>                   &lt;asp:UpdatePanel ID="UpdatePanel1" runat="server"&gt;
                            &lt;ContentTemplate&gt;
                                &lt;asp:GridView ID="GridView2" runat="server" Width="329px" AutoGenerateColumns="False"
                                    Font-Names="Arial" Font-Size="11pt" 
                                    AlternatingRowStyle-BackColor="#C2D69B" HeaderStyle-BackColor="green"
                                    AllowPaging="True" ShowFooter="True" OnPageIndexChanging="OnPaging" 

                                    Style="margin-right: 0px" BackColor="White" BorderColor="#336666" 
                                    BorderStyle="Double" BorderWidth="3px" CellPadding="3" 
                                    GridLines="Horizontal"&gt;
                                    &lt;AlternatingRowStyle BackColor="#C2D69B" /&gt;
                                    &lt;Columns&gt;
                                        &lt;asp:TemplateField&gt;
                                            &lt;ItemTemplate&gt;
                                                &lt;asp:Button ID="lnkRemove" runat="server" CommandArgument='&lt;%# Eval("il_ad")%&gt;'
                                                    OnClientClick="return confirm('S&amp;#304;LMEK &amp;#304;STED&amp;#304;&amp;#286;&amp;#304;N&amp;#304;ZDEN EM&amp;#304;N M&amp;#304;S&amp;#304;N&amp;#304;Z?')"
                                                    Text="S&amp;#304;L" OnClick="DeleteDURUM"&gt;&lt;/asp:Button&gt;
                                            &lt;/ItemTemplate&gt;
                                            &lt;FooterTemplate&gt;
                                                &lt;asp:Button ID="btnAdd" runat="server" Text="EKLE" OnClick="AddNewDURUM" /&gt;
                                            &lt;/FooterTemplate&gt;
                                        &lt;/asp:TemplateField&gt;

                                        &lt;asp:CommandField EditText="DE&amp;#286;&amp;#304;&amp;#350;T&amp;#304;R" ButtonType="Button"
                                            CancelText="&amp;#304;PTAL" DeleteText="S&amp;#304;L" UpdateText="KAYDET" ControlStyle-Width="70PX"
                                            CausesValidation="False"&gt;
                                            &lt;ControlStyle Width="70px" /&gt;
                                        &lt;/asp:CommandField&gt;
                                        &lt;asp:TemplateField ItemStyle-Width="30px" HeaderText="YTM No"&gt;
                                            &lt;ItemTemplate&gt;
                                                &lt;asp:Label ID="lblytm_id" runat="server" Text='&lt;%# Eval("ytm_id")%&gt;'&gt;&lt;/asp:Label&gt;
                                            &lt;/ItemTemplate&gt;
                                            &lt;ItemStyle Width="30px"&gt;&lt;/ItemStyle&gt;
                                        &lt;/asp:TemplateField&gt;
                                        &lt;asp:TemplateField HeaderText="&amp;#304;l"&gt;
                                            &lt;ItemTemplate&gt;
                                                &lt;asp:Label ID="il_ad" runat="server" Text='&lt;%# Eval("il_ad")%&gt;'&gt;&lt;/asp:Label&gt;
                                            &lt;/ItemTemplate&gt;
                                            &lt;EditItemTemplate&gt;
                                                &lt;asp:TextBox ID="il_ad" runat="server" Text='&lt;%# Eval("il_ad")%&gt;'&gt;&lt;/asp:TextBox&gt;
                                            &lt;/EditItemTemplate&gt;




&lt;!-- Dropdownlist is here : --&gt;
                                            &lt;FooterTemplate&gt;
                                                &lt;asp:DropDownList ID="DropDownList2" runat="server" Width= "120px" DataSourceID="iller_yukle" AutoPostBack="True"&gt;
                                                &lt;/asp:DropDownList&gt;
                                                  &lt;/FooterTemplate&gt;

                                        &lt;/asp:TemplateField&gt;
                                    &lt;/Columns&gt;
                                    &lt;FooterStyle BackColor="White" ForeColor="#333333" /&gt;
                                    &lt;HeaderStyle BackColor="#336666" Font-Bold="True" ForeColor="White" /&gt;
                                    &lt;PagerStyle BackColor="#336666" ForeColor="#000066" HorizontalAlign="Left" /&gt;
                                    &lt;RowStyle BackColor="White" ForeColor="#000066" /&gt;
                                    &lt;SelectedRowStyle BackColor="#339966" Font-Bold="True" ForeColor="White" /&gt;
                                    &lt;SortedAscendingCellStyle BackColor="#F7F7F7" /&gt;
                                    &lt;SortedAscendingHeaderStyle BackColor="#487575" /&gt;
                                    &lt;SortedDescendingCellStyle BackColor="#E5E5E5" /&gt;
                                    &lt;SortedDescendingHeaderStyle BackColor="#275353" /&gt;
                                &lt;/asp:GridView&gt;

                                &lt;/div&gt;
                            &lt;/ContentTemplate&gt;



                            &lt;Triggers&gt;
                                &lt;asp:AsyncPostBackTrigger ControlID="GridView2" /&gt;
                            &lt;asp:AsyncPostBackTrigger ControlID="DropDownList2" /&gt; &lt;!-- Error is here --&gt;

                            &lt;/Triggers&gt;
                        &lt;/asp:UpdatePanel&gt;
</code></pre>

<p>where is the mistake, I couldn't figure it out, thanks..</p>
