如何datagrid分页保持每页先前选择的checkbox的状态？

网上很多保持分页的datagird的checkbox选择状态的文章实现的是保存当前页面的chexkbox所选，也就是说第一页选择了第一条记录翻页到第二页后还是选择第一条记录，然后选择了第二条记录，再去看第一页还是第二条记录，保存的只是上次操作的结果，而我们往往希望分开保存所有页面的选择情况，下面是示例代码：

前台：

<% @ Page language = " c# "  Codebehind = " WebForm1.aspx.cs "  AutoEventWireup = " false "  Inherits = " checktest.WebForm1 "   %>
<! DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"  >
< HTML >
     < HEAD >
         < title > WebForm1 </ title >
         < meta  name ="GENERATOR"  Content ="Microsoft Visual Studio .NET 7.1" >
         < meta  name ="CODE_LANGUAGE"  Content ="C#" >
         < meta  name ="vs_defaultClientScript"  content ="JavaScript" >
         < meta  name ="vs_targetSchema"  content ="http://schemas.microsoft.com/intellisense/ie5" >
         < LINK  href ="css.css"  type ="text/css"  rel ="stylesheet" >
     </ HEAD >
     < body >
         < form  id ="Form1"  method ="post"  runat ="server" >
             < asp:datagrid  id ="DataGrid1"  runat ="server"  AutoGenerateColumns ="False"  CellSpacing ="1"  BorderWidth ="0px"
                CellPadding ="5"  CssClass ="border"  AllowPaging ="True"  PageSize ="10" >
                 < ItemStyle  CssClass ="item" ></ ItemStyle >
                 < HeaderStyle  CssClass ="header" ></ HeaderStyle >
                 < Columns >
                     < asp:TemplateColumn >
                         < ItemTemplate >
                             < asp:CheckBox  ID ="chk"  Runat ="server" ></ asp:CheckBox >
                         </ ItemTemplate >
                     </ asp:TemplateColumn >
                     < asp:BoundColumn  DataField ="CustomerID"  HeaderText ="CustomerID" ></ asp:BoundColumn >
                     < asp:BoundColumn  DataField ="CompanyName"  HeaderText ="CompanyName" ></ asp:BoundColumn >
                     < asp:BoundColumn  DataField ="ContactTitle"  HeaderText ="ContactTitle" ></ asp:BoundColumn >
                 </ Columns >
                 < PagerStyle  CssClass ="header"  Mode ="NumericPages" ></ PagerStyle >
             </ asp:datagrid >
             < asp:Button  id ="Button1"  runat ="server"  Text ="清空记录" ></ asp:Button >
         </ form >
     </ body >
</ HTML >

后台：

using  System;
using  System.Collections;
using  System.ComponentModel;
using  System.Data;
using  System.Data.SqlClient;
using  System.Drawing;
using  System.Web;
using  System.Web.SessionState;
using  System.Web.UI;
using  System.Web.UI.WebControls;
using  System.Web.UI.HtmlControls;

namespace  checktest
{
     public   class  WebForm1 : System.Web.UI.Page
    {
         protected  System.Web.UI.WebControls.Button Button1;
         protected  System.Web.UI.WebControls.DataGrid DataGrid1;
    
         private   void  Page_Load( object  sender, System.EventArgs e)
        {
             if ( ! IsPostBack)
            {
                SetBind();                
            }
        }
        
         private   void  SetBind()
        {
            SqlConnection conn = new  SqlConnection( " server=(local);uid=sa;pwd=sa
;database=Northwind " );
            SqlDataAdapter da = new  SqlDataAdapter( " select * from Customers " ,conn);
            DataSet ds = new  DataSet();
            da.Fill(ds, " table1 " );
             this .DataGrid1.DataSource = ds.Tables[ " table1 " ];
             this .DataGrid1.DataBind();            
        }

         #region  Web 窗体设计器生成的代码
         override   protected   void  OnInit(EventArgs e)
        {
             //
             //  CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
             //
            InitializeComponent();
             base .OnInit(e);
        }
        
         ///   <summary>
         ///  设计器支持所需的方法 - 不要使用代码编辑器修改
         ///  此方法的内容。
         ///   </summary>
         private   void  InitializeComponent()
        {    
             this .DataGrid1.PageIndexChanged  +=   new  System.Web.UI.WebControls.DataGridPageChangedEventHandler( this .DataGrid1_PageIndexChanged);
             this .DataGrid1.ItemDataBound  +=   new  System.Web.UI.WebControls.DataGridItemEventHandler( this .DataGrid1_ItemDataBound);
             this .Button1.Click  +=   new  System.EventHandler( this .Button1_Click);
             this .Load  +=   new  System.EventHandler( this .Page_Load);

        }
         #endregion

         private   void  DataGrid1_PageIndexChanged( object  source, System.Web.UI.WebControls.DataGridPageChangedEventArgs e)
        {
             string  data = "" ;
             foreach (DataGridItem dgi  in   this .DataGrid1.Items)
            {
                CheckBox cb = (CheckBox)dgi.FindControl( " chk " );
                 if (cb.Checked)
                    data += " 1 " ;
                 else
                    data += " 0 " ;
            }

             if (ViewState[ " pagedata " ] != null )
            {
                Hashtable ht = (Hashtable)ViewState[ " pagedata " ];
                 if (ht.Contains( this .DataGrid1.CurrentPageIndex))                
                    ht[ this .DataGrid1.CurrentPageIndex] = data;
                 else
                    ht.Add( this .DataGrid1.CurrentPageIndex,data);
                ViewState[ " pagedata " ] = ht;
            }
             else
            {
                Hashtable ht = new  Hashtable();
                ht.Add( this .DataGrid1.CurrentPageIndex,data);
                ViewState[ " pagedata " ] = ht;
            }
             this .DataGrid1.CurrentPageIndex = e.NewPageIndex;
            SetBind();
        }

         private   void  DataGrid1_ItemDataBound( object  sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
        {
             if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
            {
                 if (ViewState[ " pagedata " ] != null )
                {
                    Hashtable ht = (Hashtable)ViewState[ " pagedata " ];
                     if (ht.Contains( this .DataGrid1.CurrentPageIndex))
                    {
                        CheckBox cb = (CheckBox)e.Item.FindControl( " chk " );
                        cb.Checked = ht[ this .DataGrid1.CurrentPageIndex].ToString()[e.Item.ItemIndex].ToString() == " 1 " ;
                    }
                }
            }
        }

         private   void  Button1_Click( object  sender, System.EventArgs e)
        {
             if (ViewState[ " pagedata " ] != null )
            {
                Hashtable ht = new  Hashtable();
                ViewState[ " pagedata " ] = ht;
                SetBind();
            }
        }
    }
}

这样的话达到这样的效果，比如分页一个页面10个记录，
我们在第一页的时候选择了1，4，6记录，翻页到第二页
在第二页的时候选择了2，3，7记录，然后翻页回第一页
看到checkbox还是选择的是1，4，6记录，翻页到第二页选择2，3，7，每个页面独立保存自己的状态