title: checking multiple checkboxlist with a click of a button
body: <p>I have three different checkbox list on my web page. I want to have a checkbox that says "select All" and when that check box is checked then all three checkbox list checkboxes are checked. I was looking at this example that checks one checkbox list by clicking on select button, but I want all three checkbox list checkboxes to be checked in javascript. Below is my code</p>
  
  <pre><code> &lt;asp:CheckBox ID="chkCheckAll" runat="server" Text="Check/Uncheck All"  
                                          Style="font-weight: 700"      CausesValidation="false" oncheckedchanged="chkCheckAll_CheckedChanged" AutoPostBack="true" 
                                            /&gt;
  
     &lt;asp:CheckBoxList ID="chkList_MetricsSeverity" runat="server"   RepeatDirection="Horizontal"
                                                  RepeatColumns="3" Width="1060px"&gt;
                                              &lt;/asp:CheckBoxList&gt;
  
   &lt;asp:CheckBoxList ID="chkList_MetricsAvgMedian" runat="server" RepeatDirection="Horizontal"
                                                  RepeatColumns="3" Width="1060px"&gt;
                                              &lt;/asp:CheckBoxList&gt;
  
   &lt;asp:CheckBoxList ID="chkList_Counts" runat="server" RepeatDirection="Horizontal"
                                                  RepeatColumns="3" Width="1060px"&gt;
                                              &lt;/asp:CheckBoxList&gt;
  </code></pre>
  
  <p>any help will be appreciated</p>