Gridview Checkbox onClick event

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C#

ASP.NET

Javascript

HTML

I have a javascript which check for checkbox limit if the user select more then 3 checkbox. I can't find the onClick event for the gridview to attach my C# codings for it.

<script type="text/javascript">
            function chkCount(obj) {
                if (obj.checked == true)
                {
                    if (document.getElementById('<%=hiddenChkCount.ClientID %>').value >= 3)
                    {
                    alert('You cannot select more than 3 items.');
                    obj.checked = false;
                    }
                    else
                    {
                        document.getElementById('<%=hiddenChkCount.ClientID %>').value = parseInt(document.getElementById('<%=hiddenChkCount.ClientID %>').value) + 1;
                    }
                }
                else
                {
                    document.getElementById('<%=hiddenChkCount.ClientID %>').value = parseInt(document.getElementById('<%=hiddenChkCount.ClientID %>').value) - 1;
                }
            }
             </script>

Current Code without a "home"

protected void checkboxCOUNT(object sender, EventArgs e)
        {
            CheckBox chk;
            foreach (GridViewRow rowItem in Gv_Children.Rows)
            {
                // get reference to checkbox control placed inside the first cell of gridview control
                chk = (CheckBox)(rowItem.Cells[0].FindControl("chkSelect"));
                chk.Attributes.Add("onclick", "chkCount(this)");
            }
        }

GridView Code

<asp:GridView ID="Gv_Children" runat="server" AllowPaging="True"
                                AllowSorting="True" AutoGenerateColumns="False" BackColor="#DEBA84"
                                BorderColor="#DEBA84" BorderStyle="None" BorderWidth="1px" CellPadding="3"
                                CellSpacing="2" DataSourceID="DataSourceGuardian"
                                ShowHeaderWhenEmpty="True"
                                style="margin-right: 1px" ViewStateMode="Enabled" Width="255px"
                                >
                                <Columns>
                                    <asp:BoundField DataField="GuardianIC" HeaderText="IC" ReadOnly="True"
                                        SortExpression="GuardianIC" />
                                    <asp:BoundField DataField="Name" HeaderText="Name" SortExpression="Name" />
                                    <asp:TemplateField HeaderText="Select">
                                            <ItemTemplate>
                                                 <asp:CheckBox ID="chkSelect" runat="server" />
                                            </ItemTemplate>
                                    </asp:TemplateField>
                                </Columns>
                                <EmptyDataRowStyle BackColor="#FFF7E7" ForeColor="#8C4510" />
                                <FooterStyle BackColor="#F7DFB5" ForeColor="#8C4510" />
                                <HeaderStyle BackColor="#A55129" Font-Bold="True" ForeColor="White" />
                                <PagerStyle ForeColor="#8C4510" HorizontalAlign="Center" />
                                <RowStyle BackColor="#FFF7E7" ForeColor="#8C4510" />
                                <SelectedRowStyle BackColor="#738A9C" Font-Bold="True" ForeColor="White" />
                                <SortedAscendingCellStyle BackColor="#FFF1D4" />
                                <SortedAscendingHeaderStyle BackColor="#B95C30" />
                                <SortedDescendingCellStyle BackColor="#F1E5CE" />
                                <SortedDescendingHeaderStyle BackColor="#93451F" />
                            </asp:GridView
>