Asp.net GridView分页

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
                    CssClass="grid" AllowPaging="True" DataKeyNames="orderNO"  PageSize="5"
                    onpageindexchanged="GridView1_PageIndexChanged"
                    onpageindexchanging="GridView1_PageIndexChanging">
                    <Columns>
                        <asp:BoundField DataField="field1" HeaderText="名称" ReadOnly="True"  />
                        <asp:BoundField DataField="field2" HeaderText="名称"  />
                        <asp:BoundField DataField="field3" HeaderText="名称"  />
                        <asp:BoundField DataField="field4" HeaderText="名称"  />
                        <asp:BoundField DataField="field5" HeaderText="名称"  />
                    </Columns>
                    <PagerTemplate>
                        <br/>
                        <asp:Label ID="lblPage" runat="server" Text='<%# "第" + (((GridView)Container.NamingContainer).PageIndex + 1)  + "页/共" + (((GridView)Container.NamingContainer).PageCount) + "页" %> '></asp:Label>
                        <asp:LinkButton ID="lbnFirst" runat="Server" Text="首页"  Enabled='<%# ((GridView)Container.NamingContainer).PageIndex != 0 %>' CommandName="Page" CommandArgument="First" ></asp:LinkButton>
                        <asp:LinkButton ID="lbnPrev" runat="server" Text="上一页" Enabled='<%# ((GridView)Container.NamingContainer).PageIndex != 0 %>' CommandName="Page" CommandArgument="Prev"  ></asp:LinkButton>
                        <asp:LinkButton ID="lbnNext" runat="Server" Text="下一页" Enabled='<%# ((GridView)Container.NamingContainer).PageIndex != (((GridView)Container.NamingContainer).PageCount - 1) %>' CommandName="Page" CommandArgument="Next" ></asp:LinkButton>
                        <asp:LinkButton ID="lbnLast" runat="Server" Text="尾页"   Enabled='<%# ((GridView)Container.NamingContainer).PageIndex != (((GridView)Container.NamingContainer).PageCount - 1) %>' CommandName="Page" CommandArgument="Last" ></asp:LinkButton>
                        <br />
                    </PagerTemplate>
                </asp:GridView>

protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            BindRepeater(); 
        }
    }

    private void BindRepeater()
    {
        string userId = "1";
        DataTable dt = BankService.GetOrderListByUId(userId);
        this.GridView1.DataSource = dt;
        this.GridView1.DataBind();
    }

    protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        this.GridView1.PageIndex = e.NewPageIndex;
    }
    protected void GridView1_PageIndexChanged(object sender, EventArgs e)
    {
        BindRepeater();
    }