I have used the code:
<script type="text/javascript">
$(window).load(function () {
$(document).delegate(".checkall", "click", function(event) {
$(this).closest("table").find(':checkbox').attr('checked', this.checked);
});
});
</script>
This code is working fine when I select/deselect the checkbox in header for the first time. But when I again select the checkbox then this code is not working. The checkboxes are not selected.