title: checkboxlist check functionality
body: <p>I have a <code>CheckBoxList id="cblFiles"</code> and a <code>CheckBox id="Checkbox1"</code>. </p>
  
  <p>I have added checkAll functionality to the CheckBoxList. And now what I need to check is if any CheckBox in the CheckBoxList is unchecked "Checkbox1" should be unchecked.</p>
  
  <p>Following code doesn't work for me</p>
  
  <pre><code>function SelectNoneCheckboxes() {
      var elm = document.getElementById("&lt;%=cblFiles.ClientID %&gt;"); 
      for (i = 0; i &lt; elm.childNodes.length; i++) {
          if (elm.childNodes[i].checked == false) {
              document.getElementById("&lt;%=Checkbox1.ClientID %&gt;").checked = false;
          }
      }
  }
  </code></pre>
  
  <p>code for the checkAll Functionality</p>
  
  <pre><code>function SelectAllCheckboxes(spanChk) {
  
              var oItem = spanChk.children;
              var theBox = (spanChk.type == "checkbox") ?
          spanChk : spanChk.children.item[0];
              xState = theBox.checked;
              elm = theBox.form.elements;
  
              for (i = 0; i &lt; elm.length; i++)
                  if (elm[i].type == "checkbox" &amp;&amp;
                elm[i].id != theBox.id) {
  
  
                  if (elm[i].checked != xState)
                      elm[i].click();
  
  
              }
          }
  </code></pre>