Get the value when clicking the checkbox on the GridView

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ASP.NET

C#5.0

I have the following GridView:

<td id="TableGrid" align="left">
                    <asp:Panel ID="pnlDanhSach" Width="100%" runat="server">
                        <asp:GridView ID="grvDanhSach" OnPageIndexChanging="grvDanhSach_PageIndexChanging" AutoGenerateColumns="False" SkinID="SkinDefault" BorderStyle="None" BorderWidth="1px"
                            Width="100%" runat="server">
                            <Columns>
                                <asp:TemplateField>
                                    <HeaderTemplate>
                                        <asp:CheckBox ID="chkHeader" runat="server" />
                                    </HeaderTemplate>
                                    <ItemTemplate>
                                        <asp:CheckBox ID="chkRow" runat="server" />
                                    </ItemTemplate>
                                    <HeaderStyle Width="40px" HorizontalAlign="Center" />
                                </asp:TemplateField>
                                <asp:TemplateField HeaderStyle-HorizontalAlign="Center" HeaderText="UserName" 
                                    SortExpression="UserName" Visible="False">
                                    <ItemTemplate>
                                        <asp:Label ID="lblUserName" runat="server" Text='<%# Bind("UserName") %>'></asp:Label>
                                    </ItemTemplate>
                                </asp:TemplateField>
                                <asp:BoundField DataField="HoVaTen" HeaderText="Họ và tên" 
                                    SortExpression="HoVaTen" />
                                <asp:BoundField DataField="RoleName" HeaderText="Quyền hạn" 
                                    SortExpression="RoleName" />
                                <asp:BoundField DataField="TenPhong" HeaderText="Phòng ban" 
                                    SortExpression="TenPhong" />
                            </Columns>
                        </asp:GridView>
                    </asp:Panel>
                </td>

I use jQuery to check / uncheckall

<script type="text/javascript">
        $("[id*=chkHeader]").live("click", function () {
            var chkHeader = $(this);
            var grid = $(this).closest("table");
            $("input[type=checkbox]", grid).each(function () {
                if (chkHeader.is(":checked")) {
                    $(this).attr("checked", "checked");
                    $("td", $(this).closest("tr")).addClass("selected");
                } else {
                    $(this).removeAttr("checked");
                    $("td", $(this).closest("tr")).removeClass("selected");
                }
            });
        });
        $("[id*=chkRow]").live("click", function () {
            var grid = $(this).closest("table");
            var chkHeader = $("[id*=chkHeader]", grid);
            if (!$(this).is(":checked")) {
                $("td", $(this).closest("tr")).removeClass("selected");
                chkHeader.removeAttr("checked");
            } else {
                $("td", $(this).closest("tr")).addClass("selected");
                if ($("[id*=chkRow]", grid).length == $("[id*=chkRow]:checked", grid).length) {
                    chkHeader.attr("checked", "checked");
                }
            }
        });
</script>

In behide code I get the following:

private string GetUserDoc()
    {
        int intNumCheck = 0;
        string strUserDoc = "";
        if (grvDanhSach.Rows.Count > 0)
        {
            for (int i = 0; i < grvDanhSach.Rows.Count; i++)
            {
                CheckBox chkChon = (CheckBox)grvDanhSach.Rows[i].FindControl("chkRow");
                Label lblUserName = (Label)grvDanhSach.Rows[i].FindControl("lblUserName");
                if (chkChon.Checked == true)
                {
                    strUserDoc = lblUserName.Text + "|";
                    intNumCheck++; 
                }
                else
                {
                    ScriptManager.RegisterStartupScript(this, this.GetType(), "Alert", "alert('Bạn cần chọn ít nhất một cán bộ');", true);
                }
                if (intNumCheck > 1)
                {
                    strUserDoc += lblUserName.Text + "|";
                }
            }
        }
        return strUserDoc;
    }

but when I check the checkbox, then it does not understand and jump to the else statement. Do not know when to use jQuery it understands their value checks are not right. Who knows just me with. Thank you.