gridview中添加checkbox(javascript)

<script language="javascript">
       function SelectAll(tempControl)
       {
         var theBox=tempControl;
         xState=theBox.checked;
        
         elem=theBox.form.elements;
         for(i=0;i<elem.length;i++)
         if(elem[i].type=="checkbox"&& elem[i].id!=theBox.id)
            {
              if(elem[i].checked!=xState)
              elem[i].click();
              }
       }
</script>
.................

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<FooterTemplate>
  <input id="chkFooter"  type=checkbox />??
</FooterTemplate>