用JavaScript获取GridView的ItemTemplate的CheckBox全选或全部取消？

Question

 <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" Width="770px"                        OnDataBound="GridView1_DataBound">                        <Columns>                            <asp:TemplateField HeaderText="选择">                                <EditItemTemplate>                                    <asp:CheckBox ID="CheckBox1" runat="server" />                                </EditItemTemplate>                                <HeaderTemplate>                                    <input type="checkbox" id="checkbox_1" onclick="Check()" />全选                                </HeaderTemplate>                                <ItemTemplate>                                    <asp:CheckBox ID="CB_Item" runat="server" />                                </ItemTemplate>                                <ItemStyle HorizontalAlign="Center" />                            </asp:TemplateField>