datagrid加checkbox实现分页不丢失选择的记录

namespace checkboc_page
{
 /// <summary>
 /// WebForm1 的摘要说明。
 /// </summary>
 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(!Page.IsPostBack)
   {
    show();
   }
  }

  private void show()
  {
   string conn =  ConfigurationSettings.AppSettings.Get("Connstring");
   DataSet ds = new DataSet();
   using(  SqlConnection con = new SqlConnection(conn))
   {
    con.Open();
    SqlCommand comm = new SqlCommand();
    SqlDataAdapter da =new SqlDataAdapter();
    
    da.SelectCommand = new SqlCommand();
    da.SelectCommand.Connection = con;
    da.SelectCommand.CommandText = "select * from Orders";
    da.SelectCommand.CommandType = CommandType.Text;
    
    da.Fill(ds);
           
   
    
   }
   this.DataGrid1.DataSource = ds.Tables[0];
  
   this.DataGrid1.DataBind();
            
   if(Session["userlist"]!=null)
   {
    Hashtable ht =(Hashtable) Session["userlist"];
    if(ht!=null)
    {
     for(int i = 0 ;i<DataGrid1.Items.Count ;i++)
     {
      if (ht.ContainsKey(DataGrid1.Items[i].Cells[0].Text.ToString().Trim()))
       (DataGrid1.Items[i].Cells[2].FindControl("CheckBox1") as CheckBox).Checked = true;

     }
    }
   }
  }

  private void check()
  {
   Hashtable ht = new Hashtable();
   if(Session["userlist"]!=null)
   {
    ht =(Hashtable) Session["userlist"];
    if(ht!=null)
    {
     for(int i = 0 ;i<DataGrid1.Items.Count ;i++)
     {
      if ( (DataGrid1.Items[i].Cells[2].FindControl("CheckBox1") as CheckBox).Checked)
      {
       if (! ht.ContainsKey(DataGrid1.Items[i].Cells[0].Text.ToString().Trim()))
       {
        ht.Add(DataGrid1.Items[i].Cells[0].Text.ToString().Trim(),DataGrid1.Items[i].Cells[1].Text.ToString().Trim());
       }
      }
      else
      {
       if ( ht.ContainsKey(DataGrid1.Items[i].Cells[0].Text.ToString().Trim()))
       {
        ht.Remove(DataGrid1.Items[i].Cells[0].Text.ToString().Trim());
       }
      }
     }
    }
   }
   else
   {
    for(int i = 0 ;i<DataGrid1.Items.Count ;i++)
    {
     if ( (DataGrid1.Items[i].Cells[2].FindControl("CheckBox1") as CheckBox).Checked)
     {
      ht.Add(DataGrid1.Items[i].Cells[0].Text.ToString().Trim(),DataGrid1.Items[i].Cells[1].Text.ToString().Trim());
     }
    }
   }

   Session["userlist"] = ht;
  }

  #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.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)
  {
   check();
   
   DataGrid1.CurrentPageIndex = e.NewPageIndex;
   show();
  }

  private void Button1_Click(object sender, System.EventArgs e)
  {
   
   
             check();
   Hashtable ht = (Hashtable)Session["userlist"];
   
    foreach (DictionaryEntry objDE in ht)
    {
     Response.Write(objDE.Value.ToString());
     
    }

   
  }
 }
}