对象定义被隐藏是什么意思

别人做的一半的项目，我随便贴点代码上来，分页这块，总是提示对象定义被隐藏是什么意思啊 private void SetddlPageNumInfo()
    {        this.ddlPageNum.Items.Clear();
        this.ddlPageNum1.Items.Clear();
        // 总页数小于1
        if (int.Parse(this.lbTotalPage.Text) <= 1)
        {            this.lblPrompt01.Visible = this.lblPrompt02.Visible = false;
            this.lblPrompt11.Visible = this.lblPrompt12.Visible = false;
            this.ddlPageNum.Visible = this.ddlPageNum1.Visible = false;
        }
        else
        {
            for (int i = 1; i <= Int32.Parse(lbTotalPage.Text); i++)
            {
                ListItem item = new ListItem();
                item.Text = item.Value = (i).ToString();
                this.ddlPageNum.Items.Add(item);
                this.ddlPageNum1.Items.Add(item);
            }
            this.ddlPageNum.SelectedIndex = this.ddlPageNum.Items.IndexOf(this.ddlPageNum.Items.FindByValue(pageIndex.ToString()));
            this.ddlPageNum1.SelectedIndex = this.ddlPageNum1.Items.IndexOf(this.ddlPageNum1.Items.FindByValue(pageIndex.ToString()));
        }
    }
<table bgcolor="#e6e6e6" border="0" cellpadding="0" cellspacing="0" width="100%">
                            <tr align="center">
                                <asp:LinkButton ID="lbFirstPage" runat="server" CommandArgument="first" OnCommand="PageIndexChange">首页</asp:LinkButton>
                                <asp:LinkButton ID="lbPrevPage" runat="server" CommandArgument="prev" OnCommand="PageIndexChange">上一页</asp:LinkButton>
                                <asp:LinkButton ID="lbNextPage" runat="server" CommandArgument="next" OnCommand="PageIndexChange">下一页</asp:LinkButton>
                                <asp:LinkButton ID="lbLastPage" runat="server" CommandArgument="last" OnCommand="PageIndexChange">尾页</asp:LinkButton>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
                                <asp:Label ID="lblPrompt01" runat="server">跳转到：第</asp:Label>
                                <asp:DropDownList ID="ddlPageNum" runat="server" AutoPostBack="True" Width="58" OnSelectedIndexChanged="ddlPageNum_SelectedIndexChanged">
                                </asp:DropDownList>
                                <asp:Label ID="lblPrompt02" runat="server">&nbsp;页</asp:Label>
                            </tr>
                        </table>