asp.net Repeater显示父子表数据,无闪烁

using System;
using System.Data;
using System.Configuration;
using System.Collections;
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;

namespace RepeaterTest
{
public partial class Repeater : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
this.bind();
}
}

private DataSet dataSource
{
get
{
if (ViewState["ds"] != null)
{
return (DataSet)ViewState["ds"];
}
else
{
DataSet ds = DataSource.GetDataSet();
ViewState["ds"] = ds;
return ds;
}
}
}

private void bind()
{
DataSet ds = this.dataSource;

this.Repeater1.DataSource = ds.Tables["tbclass"];
this.Repeater1.DataBind();

this.Repeater2.DataSource = ds.Tables["tbclass"];
this.Repeater2.DataBind();
}

protected void Repeater1_ItemCommand(object source, RepeaterCommandEventArgs e)
{
if (e.CommandName == "expand")
{
LinkButton btn = (LinkButton)e.CommandSource;
GridView grid =(GridView)btn.Parent.FindControl("grid1");
if (btn.Text == "+")
{
btn.Text = "-";
grid.Visible = true;
}
else
{
btn.Text = "+";
grid.Visible = false;
}
}
}

protected void Repeater1_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
DataTable dt = this.dataSource.Tables["tbstu"];
LinkButton objButton = (LinkButton)e.Item.FindControl("btnExpand");
if (objButton != null && objButton.CommandArgument !="")
{
string classID = objButton.CommandArgument;
dt.DefaultView.RowFilter = "ClassID=" + classID;
DataTable dtStu = dt.DefaultView.ToTable();

GridView grid = (GridView)e.Item.FindControl("grid1");
grid.DataSource = dtStu;
grid.DataBind();
}
}

protected void Repeater2_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
DataTable dt = this.dataSource.Tables["tbstu"];
Label objlbl = (Label)e.Item.FindControl("lblclassid");
if (objlbl != null && objlbl.Text != "")
{
string classID = objlbl.Text;
dt.DefaultView.RowFilter = "ClassID=" + classID;
DataTable dtStu = dt.DefaultView.ToTable();

GridView grid = (GridView)e.Item.FindControl("grid2");
grid.DataSource = dtStu;
grid.DataBind();
}
}
}
}