title: Trigger updatePanel with radiobutton SelectedIndexChanged
body: <p>I have a radiobutton list (With 2 rdb) and a check list (7 ckb). I would like the checkbox list appears only when the user selects the second radio button is checked.</p>
  
  <p>I never used AJAX before.</p>
  
  <p>My actual code (yes, they are inside a table):</p>
  
  <pre><code>&lt;td&gt;
  
                      &lt;asp:Label ID="Label7" runat="server" Font-Bold="True"&gt;Frequency&lt;/asp:Label&gt;
                      &lt;table&gt;
                          &lt;tr&gt;
                              &lt;td&gt;
                                  &lt;asp:RadioButtonList ID="rdbDaysList" runat="server" AutoPostBack="True" OnSelectedIndexChanged="rdbDaysList_SelectedIndexChanged"
                                      RepeatColumns="2" CausesValidation="True"&gt;
                                      &lt;asp:ListItem&gt;Daily&lt;/asp:ListItem&gt;
                                      &lt;asp:ListItem&gt;Weekly&lt;/asp:ListItem&gt;
                                  &lt;/asp:RadioButtonList&gt;
                              &lt;/td&gt;
                          &lt;/tr&gt;
                          &lt;tr&gt;
                              &lt;td class="style3"&gt;
                                  &lt;asp:CheckBoxList ID="ckbList" runat="server" Visible="false" RepeatColumns="5" RepeatDirection="Horizontal"&gt;
                                      &lt;asp:ListItem&gt;Monday&lt;/asp:ListItem&gt;
                                      &lt;asp:ListItem&gt;Tuesday&lt;/asp:ListItem&gt;
                                      &lt;asp:ListItem&gt;Wednesday&lt;/asp:ListItem&gt;
                                      &lt;asp:ListItem&gt;Thursday&lt;/asp:ListItem&gt;
                                      &lt;asp:ListItem&gt;Friday&lt;/asp:ListItem&gt;
                                      &lt;asp:ListItem&gt;Saturday&lt;/asp:ListItem&gt;
                                      &lt;asp:ListItem&gt;Sunday&lt;/asp:ListItem&gt;
                                  &lt;/asp:CheckBoxList&gt;
                              &lt;/td&gt;
                          &lt;/tr&gt;
                      &lt;/table&gt;
  &lt;/td&gt;
  </code></pre>
  
  <p>Thanks in advance!</p>