asp.net中GridView全選後進行大量刪除

    <form id="form1" runat="server">
    <asp:Button ID="Delall" runat="server" Text="刪除選中" onclick="Delall_Click" />
    <div>
        <asp:GridView ID="gvUser" runat="server"
            AutoGenerateColumns="False" DataKeyNames="UserId"
            DataSourceID="ObjectDataSourceUser" onrowdeleted="gvUser_RowDeleted"
            CellPadding="4" ForeColor="#333333" GridLines="None" AllowPaging="True"
            PageSize="3">
            <AlternatingRowStyle BackColor="White" ForeColor="#284775" />

            <Columns>
                 <asp:TemplateField>
                      <HeaderTemplate>
                            <input id="CheckAll" type="checkbox" onclick="selectAll(this);" />全選
                      </HeaderTemplate>
                      <ItemTemplate>
                            <asp:CheckBox runat="server" ID="CheckSingle" />
                      </ItemTemplate>
                      <ItemStyle Width="100px" />

                 </asp:TemplateField>

                <asp:BoundField DataField="UserId" HeaderText="UserId"
                    SortExpression="UserId" />
                <asp:BoundField DataField="UserName" HeaderText="UserName"
                    SortExpression="UserName" />
                <asp:BoundField DataField="UserPass" HeaderText="UserPass"
                    SortExpression="UserPass" />
                <asp:BoundField DataField="Role" HeaderText="Role" SortExpression="Role" />
                <asp:BoundField DataField="RegTime" HeaderText="RegTime"
                    SortExpression="RegTime" />
                <asp:BoundField DataField="LogNum" HeaderText="LogNum"
                    SortExpression="LogNum" />
                <%--<asp:CommandField  ShowEditButton="True"  />--%>
                <asp:TemplateField>
                                <EditItemTemplate>
                                    <asp:LinkButton ID="LinkButton4" runat="server" CommandName="update">更新</asp:LinkButton>
                                    <asp:LinkButton ID="LinkButton5" runat="server" CommandName="cancel">取消</asp:LinkButton>
                                </EditItemTemplate>
                                <ItemTemplate>
                                    <asp:LinkButton ID="LinkButton3" runat="server" CommandName="Edit">編輯</asp:LinkButton>
                                </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="操作" ShowHeader="False">
                    <ItemTemplate>
                        <asp:LinkButton ID="lbDelete" runat="server" CausesValidation="False"
                            OnClientClick="return confirm('你確定要刪除嗎?')"  Text="刪除" CommandName="Delete" ></asp:LinkButton>
                    </ItemTemplate>
                    <HeaderStyle ForeColor="#0033CC" />
                    <ItemStyle HorizontalAlign="Center" VerticalAlign="Middle" />
                </asp:TemplateField>
            </Columns>
            <EditRowStyle BackColor="#999999" />
            <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" />
            <HeaderStyle BackColor="Black" Font-Bold="True" ForeColor="White" />
            <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" />
            <RowStyle BackColor="#F7F6F3" ForeColor="#333333" />
            <SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" />
            <SortedAscendingCellStyle BackColor="#E9E7E2" />
            <SortedAscendingHeaderStyle BackColor="#506C8C" />
            <SortedDescendingCellStyle BackColor="#FFFDF8" />
            <SortedDescendingHeaderStyle BackColor="#6F8DAE" />
        </asp:GridView>
        <asp:ObjectDataSource ID="ObjectDataSourceUser" runat="server"
            DataObjectTypeName="User" DeleteMethod="DeleteUser" InsertMethod="AddUser"
            SelectMethod="GetAllUsers" TypeName="UserService" UpdateMethod="ModifyUser">
        </asp:ObjectDataSource>
    </div>
    </form>
     <script type="text/javascript">
         function selectAll(obj) {
             var chkall = obj;
             State = chkall.checked;
             elem = chkall.form.elements;
             for (i = 0; i < elem.length; i++) {
                 if (elem[i].type == "checkbox" && elem[i] != chkall.id) {
                     if (elem[i].checked != State) {
                         elem[i].click();
                     }
                 }
             }
         }

</script>

    protected void Delall_Click(object sender, EventArgs e)
    {
        int intCount = this.gvUser.Rows.Count;
        for (int i = 0; i < intCount; i++)
        {
            CheckBox CheckSingle = this.gvUser.Rows[i].Cells[0].FindControl("CheckSingle") as CheckBox;
            if (CheckSingle.Checked)
            {
                UserService.DeleteUserByUserId(Convert.ToInt16(this.gvUser.DataKeys[i].Values[0]));
            }
        }
        //刪除後的更新
        gvUser.DataBind();
    }