用下拉列表控制gridview的分页

aspx.cs中：

protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
        {
            GridView1.PageIndex = e.NewPageIndex;
            GridView1.DataBind();
        }
        protected void PageDropDownList_SelectedIndexChanged(object sender,EventArgs e)
        {
           
            GridViewRow GVRow = GridView1.TopPagerRow;
            DropDownList DDList = (DropDownList)GVRow.Cells[0].FindControl("PageDropDownList");
            GridView1.PageIndex = DDList.SelectedIndex;

            GridViewRow pagerRow = GridView1.BottomPagerRow;
            DropDownList DDList1 = (DropDownList)pagerRow.Cells[0].FindControl("PageDropDownList");
            GridView1.PageIndex = DDList1.SelectedIndex;
            GridView1.DataBind();
        }
        protected void GridView1_DataBound(object sender, EventArgs e)
        {
            try
            {
                GridViewRow pagerRow1 = GridView1.BottomPagerRow;
                GridViewRow pagerRow = GridView1.TopPagerRow;

                LinkButton linkBtnFirst = (LinkButton)pagerRow.Cells[0].FindControl("linkBtnFirst");
                LinkButton linkBtnPrev = (LinkButton)pagerRow.Cells[0].FindControl("linkBtnPrev");
                LinkButton linkBtnNext = (LinkButton)pagerRow.Cells[0].FindControl("linkBtnNext");
                LinkButton linkBtnLast = (LinkButton)pagerRow.Cells[0].FindControl("linkBtnLast");
                if (GridView1.PageIndex == 0)
                {
                    linkBtnFirst.Enabled = false;
                    linkBtnPrev.Enabled = false;
                }
                else if (GridView1.PageIndex == GridView1.PageCount - 1)
                {
                    linkBtnLast.Enabled = false;
                    linkBtnNext.Enabled = false;
                }
                else if (GridView1.PageCount <= 0)
                {
                    linkBtnFirst.Enabled = false;
                    linkBtnPrev.Enabled = false;
                    linkBtnNext.Enabled = false;
                    linkBtnLast.Enabled = false;
                }
                LinkButton linkBtnFirst1 = (LinkButton)pagerRow1.Cells[0].FindControl("linkBtnFirst");
                LinkButton linkBtnPrev1 = (LinkButton)pagerRow1.Cells[0].FindControl("linkBtnPrev");
                LinkButton linkBtnNext1 = (LinkButton)pagerRow1.Cells[0].FindControl("linkBtnNext");
                LinkButton linkBtnLast1 = (LinkButton)pagerRow1.Cells[0].FindControl("linkBtnLast");
                if (GridView1.PageIndex == 0)
                {
                    linkBtnFirst1.Enabled = false;
                    linkBtnPrev1.Enabled = false;
                }
                else if (GridView1.PageIndex == GridView1.PageCount - 1)
                {
                    linkBtnLast1.Enabled = false;
                    linkBtnNext1.Enabled = false;
                }
                else if (GridView1.PageCount <= 0)
                {
                    linkBtnFirst1.Enabled = false;
                    linkBtnPrev1.Enabled = false;
                    linkBtnNext1.Enabled = false;
                    linkBtnLast1.Enabled = false;
                }

                DropDownList pageList = (DropDownList)pagerRow.Cells[0].FindControl("PageDropDownList");
                Label pageLabel = (Label)pagerRow.Cells[0].FindControl("CurrentPageLabel");

                DropDownList pageList1 = (DropDownList)pagerRow1.Cells[0].FindControl("PageDropDownList");
                Label pageLabel1 = (Label)pagerRow1.Cells[0].FindControl("CurrentPageLabel");
                if (pageList != null && pageList1!=null)
                {
                    for (int i = 0; i < GridView1.PageCount; i++)
                    {
                        int pageNumber = i + 1;
                        ListItem item = new ListItem(pageNumber.ToString() + "/" + GridView1.PageCount.ToString(), pageNumber.ToString());
                        if (i == GridView1.PageIndex)
                        {
                            item.Selected = true;
                        }
                        pageList.Items.Add(item);
                        pageList1.Items.Add(item);
                    }
                }

                if (pageLabel != null)
                {
                    int currentPage = GridView1.PageIndex + 1;
                    pageLabel.Text = pageLabel1.Text = "当前页： " + currentPage.ToString() +
                      " / " + GridView1.PageCount.ToString();
                }
            }
            catch
            {
                Label1.Text = "尚无数据。";
            }
        }

aspx中:
<div style="overflow-x: auto;overflow-y: auto;height: 300px;1000px">
                        <asp:GridView ID="GridView1" runat="server" AllowPaging="True" PageSize="15" Width="207px" OnPageIndexChanging="GridView1_PageIndexChanging" OnDataBound="GridView1_DataBound" CellPadding="0" EnableViewState="False" UseAccessibleHeader="False">
                        <PagerSettings Position="TopAndBottom" />
                        <PagerTemplate>
                <table width="900">
                    <tr height="20">
                        <td width="70%" align="left">
                            <asp:Label ID="CurrentPageLabel" runat="server"></asp:Label>
                        </td>
                        <td width="70%">
                            <asp:LinkButton CommandName="Page" CommandArgument="First" ID="linkBtnFirst" runat="server">首页</asp:LinkButton>
                            <asp:LinkButton CommandName="Page" CommandArgument="Prev" ID="linkBtnPrev" runat="server">上一页</asp:LinkButton>
                            <asp:LinkButton CommandName="Page" CommandArgument="Next" ID="linkBtnNext" runat="server">下一页</asp:LinkButton>
                            <asp:LinkButton CommandName="Page" CommandArgument="Last" ID="linkBtnLast" runat="server">末页</asp:LinkButton>
                            <asp:Label ID="MessageLabel" ForeColor="Blue" Text="页码:" runat="server" />
                            <asp:DropDownList ID="PageDropDownList" AutoPostBack="true" OnSelectedIndexChanged="PageDropDownList_SelectedIndexChanged" runat="server" />
                        </td>
                    </tr>
                </table>
            </PagerTemplate>
                        </asp:GridView>
                        </div>