UpdatePanel中GridView的分页问题

     protected   void  GridView1_PageIndexChanging( object  sender, GridViewPageEventArgs e)
     {
        GridView1.PageIndex = e.NewPageIndex;

        GridView1.DataSource = getDt();

        GridView1.DataBind();
    }

< asp:Button  ID ="Button1"  runat ="server"  OnClick ="Button1_Click"  Text ="Button"  PostBackUrl ="~/Default.aspx"    />

<% @ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default"  %>

<% @ Register Assembly="C1.Web.C1WebGrid.2" Namespace="C1.Web.C1WebGrid" TagPrefix="C1WebGrid"  %>

<% @ Register Assembly="Microsoft.Web.Atlas" Namespace="Microsoft.Web.UI" TagPrefix="cc1"  %>

<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >

< html  xmlns ="http://www.w3.org/1999/xhtml"   >
< head  runat ="server" >
     < title > 无标题页 </ title >
</ head >
< body >
     < form  id ="form1"  runat ="server" >
     < div >
         < cc1:ScriptManager  ID ="ScriptManager1"  runat ="server"  EnablePartialRendering ="True" >
             < ErrorTemplate >
                 < div  style ="padding: 12px; width: 400px; height: 140px; border: #000000 1px solid;
                    background-color: white; text-align: left" >
                    An error has occurred: < br  />
                     < span  id ="errorMessageLabel"  runat ="server" ></ span >
                     < br  />
                     < br  />
                     < input  id ="okButton"  runat ="server"  type ="button"  value ="OK"   />
                
             </ ErrorTemplate >
         </ cc1:ScriptManager >
         &nbsp; </ div >
         < cc1:UpdatePanel  ID ="UpdatePanel1"  runat ="server" >
             < ContentTemplate >
         < asp:Button  ID ="Button1"  runat ="server"  OnClick ="Button1_Click"  Text ="Button"  PostBackUrl ="~/Default.aspx"    />
         < asp:GridView  ID ="GridView1"  runat ="server"  AllowPaging ="True"  AllowSorting ="True"  AutoGenerateColumns ="False"  OnPageIndexChanging ="GridView1_PageIndexChanging" >
             < Columns >
                 < asp:TemplateField >
                     < ItemTemplate >
                         < asp:TextBox  ID ="TextBox1"  runat ="server"  Text =<%#  Eval("id") % > > </ asp:TextBox >
                     </ ItemTemplate >
                 </ asp:TemplateField >
                 < asp:TemplateField >
                     < ItemTemplate >
                         < asp:TextBox  ID ="TextBox2"  runat ="server"  Text =<%#  Eval("name") % > > </ asp:TextBox >
                     </ ItemTemplate >
                 </ asp:TemplateField >
                 < asp:BoundField  DataField ="name"   />
             </ Columns >
         </ asp:GridView >
             </ ContentTemplate >
         </ cc1:UpdatePanel >
         </ div >
     </ form >
</ body >
</ html >

using  System;
using  System.Data;
using  System.Configuration;
using  System.Web;
using  System.Web.Security;
using  System.Web.UI;
using  System.Web.UI.WebControls;
using  System.Web.UI.WebControls.WebParts;
using  System.Web.UI.HtmlControls;

public  partial  class  _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            //this.GridView1.DataSource = this.getDt();
            //this.GridView1.DataBind();
        }
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        this.GridView1.DataSource = this.getDt(); 
        this.GridView1.DataBind();
    }

    private DataTable getDt()
    {
        DataTable dt = new DataTable();
        dt.Columns.Add("id");
        dt.Columns.Add("name");

        DataRow dr = null;
        for (int i = 0; i < 20; i++)
        {
            dr = dt.NewRow();
            dr["id"] = i.ToString();
            dr["name"] = "名字" + i.ToString();

            dt.Rows.Add(dr);
        }

        return dt;
    }
    protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        GridView1.PageIndex = e.NewPageIndex;

        GridView1.DataSource = getDt();

        GridView1.DataBind();
    }
}