title: How to prevent ajax toolkit DropDownExtender from closing on click?
body: <p>I have the code below to implement a dropdownlist with checkboxes.  My problem is that every time i click a checkbox the dropdownlist closes and i need to reopen it to select more checkboxes.  How do i make it so the dropdownlist dosn't close until i click off of it?</p>
  
  <pre><code>    &lt;asp:Panel ID="pnl_Items" runat="server" BorderColor="Aqua" BorderWidth="1"&gt;
          &lt;asp:CheckBoxList ID="cbl_Items" runat="server"&gt;
              &lt;asp:ListItem Text="Item 1" /&gt;
              &lt;asp:ListItem Text="Item 2" /&gt;
              &lt;asp:ListItem Text="Item 3" /&gt;          
          &lt;/asp:CheckBoxList&gt;
      &lt;/asp:Panel&gt;
  
     &lt;br /&gt;
      &lt;asp:TextBox ID="tb_Items" runat="server"&gt;&lt;/asp:TextBox&gt;
      &lt;ajax:DropDownExtender  ID="TextBox1_DropDownExtender" 
                              runat="server" 
                              DynamicServicePath="" 
                              Enabled="True" 
                              DropDownControlID="pnl_Items" on 
                              TargetControlID="tb_Items"&gt;
      &lt;/ajax:DropDownExtender&gt;
  </code></pre>