Header checkbox on checking not makin all the child child check boxes checked

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C#

ASP.NET

Javascript

Hi,

I am suffering from a very unusual problem. I wrote a java script which was working fine earlier making all the check boxes checked if I select the header checkbox in grid view but than when I added other functionality and controls to my page it stopped working. I am unable to guess why is it happening. My code of javascript is :-

function SelectAll(id) {

        var frm = document.forms[0];

        for (i=0;i<frm.elements.length;i++) {

            if (frm.elements[i].type == "checkbox") {

                frm.elements[i].checked = document.getElementById(id).checked;

            }

        }

    }  

and c# code for the same is:

if (e.Row.RowType == DataControlRowType.Header)
       {

           ((CheckBox)e.Row.FindControl("chkAll")).Attributes.Add("onclick", "javascript:SelectAll('" + ((CheckBox)e.Row.FindControl("chkAll")).ClientID + "')");
       }

Please help guyz !