Selecting all Checkboxes within gridview

Hi friends,
 As we know while developing code for application we need to do lots of customization according to client requirement.,
So today i'm sharing some gridview concepts
when in gridview of web page contains checkbox,& if client's requirement is to select or unselect all rows of data by selecting or unselecting header checkbox. for this we need to write javascript code that will do this task.
I'm giving some syntax for that.
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script>

<script type="text/javascript">
        function SelectAllCheckboxes(chk) {
            $('#<%=gvSubject.ClientID %>').find("input:checkbox").each(function()
             {
                if (this != chk) {
                    this.checked = chk.checked;
                }
            });
        }
    </script>