title: Page with 2 Listboxes OnSelectedIndexChanged is firing the same listbox
body: <p>I have web page which is ContentPage of MasterPages and it has 2 ListBoxes with many items inside.
  The code for the 1st Listbox is</p>
  
  <pre><code>&lt;div id="electrics" class="panel-collapse collapse"&gt;
      &lt;div class="panel-body"&gt;
          &lt;asp:UpdatePanel ID="UpdatePanel7" runat="server" UpdateMode="Conditional"&gt;
              &lt;ContentTemplate&gt;
                  &lt;asp:ListBox ID="ListBox5" runat="server" CssClass="form-control" Font-Size="12pt" AutoPostBack="True" OnSelectedIndexChanged="ListBox5_SelectedIndexChanged"&gt;&lt;/asp:ListBox&gt;
                  &lt;asp:UpdateProgress ID="UpdateProgress3" runat="server" AssociatedUpdatePanelID="UpdatePanel7"&gt;
                      &lt;ProgressTemplate&gt;
                          &lt;asp:Image ID="Image1112" runat="server" ImageUrl="images/ajax.gif" /&gt;
                      &lt;/ProgressTemplate&gt;
                  &lt;/asp:UpdateProgress&gt;
              &lt;/ContentTemplate&gt;
              &lt;Triggers&gt;
                  &lt;asp:AsyncPostBackTrigger ControlID="ListBox5" /&gt;
              &lt;/Triggers&gt;
          &lt;/asp:UpdatePanel&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>The code for the second is the same only change the ID.</p>
  
  <p>When i click the listbox the code open a webpage with parameters from the selected listbox.</p>
  
  <p>The page shows OK and the parameters are showing correct.</p>
  
  <p>When I press back and select the second Listbox, it fires again the first listbox so the new webpage shows the same parameters from the first listbox.</p>
  
  <p>This is the problem, the second listbox is not firing, its only fires the first clicked. 
  I have to reload the page to be able to click the second listbox.</p>