title: ASP.NET AJAX UpdatePanel drop down list issue
body: <p>I have 2 drop-down lists (DDL), and below them an asp.net ajax updatepanel which I want to update/refresh based on selections in the 2 DDL.
  The second DDL's contents are dependent on what was selected in the first DDL.</p>
  
  <p>The issue is that if I select something in the first DDL, it doesn't populate the second DDL, but without the ajax updatepanel it works perfectly. Please assist if possible. Below is the code. Thanks.</p>
  
  <pre><code>&lt;asp:DropDownList runat="server" ID="ddlPrimary" AutoPostBack="true" OnSelectedIndexChanged="ddlPrimary_SelectedIndexChanged"&gt;&lt;/asp:DropDownList&gt;
  &lt;asp:DropDownList runat="server" ID="ddlSecondary" AutoPostBack="true" OnSelectedIndexChanged="ddlSecondary_SelectedIndexChanged"&gt;&lt;/asp:DropDownList&gt;
  
  &lt;asp:ScriptManager ID="sm" runat="server"&gt;&lt;/asp:ScriptManager&gt;
  &lt;asp:UpdatePanel ID="up" runat="server"&gt;
      &lt;ContentTemplate&gt;
           &lt;!-- asp.net repeater with table --&gt;
           &lt;tr&gt;
                &lt;td&gt;
                    &lt;asp:Label runat="server" ID="lblProdCode" Text='&lt;%# Eval("ProdCode") %&gt;'&gt;&lt;/asp:Label&gt;
                &lt;/td&gt;
                &lt;td&gt;
                    &lt;asp:Label runat="server" ID="lblProdDesc" Text='&lt;%# Eval("ProdDesc") %&gt;'&gt;&lt;/asp:Label&gt;
            &lt;/tr&gt;
      &lt;/ContentTemplate&gt;
      &lt;Triggers&gt;
                  &lt;asp:AsyncPostBackTrigger ControlID="ddlPrimary" EventName="SelectedIndexChanged" /&gt;
                  &lt;asp:AsyncPostBackTrigger ControlID="ddlSecondary" EventName="SelectedIndexChanged" /&gt;
       &lt;/Triggers&gt;
   &lt;/asp:UpdatePanel&gt; 
  </code></pre>