输出excel页面自动关闭，无提示“打开”“保存”“取消”对话框
直接运行这个页面，如果在本页设置reportid = "28"，直接运行本页面可以提示保存，如果不赋值直接运行本页面也能正常打印出设置的错误提示，但如果是从其他页面提交的数据过来，不论有没有在该页面设置初始值都是一样的情况，新打开的页面闪一下就自动关闭了，没有任何提示！

我的源文件如下：
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Net;
using System.IO;

public partial class ExportExcel : System.Web.UI.Page
{
  protected void Page_Load(object sender, EventArgs e)
  {
  if (!Page.IsPostBack)
  {
  try
  {
  string reportid = Request.Form["reportid"];
  reportid = "28";
  if (reportid == "")
  {
  Response.Write("页面错误");
  }
  else
  {
  //Response.Write(reportid);
  Maticsoft.OAchargeReportTitle getTle = new Maticsoft.OAchargeReportTitle();
  DataSet getTINFO = getTle.GetList("id=" + reportid);
  string reportTile = getTINFO.Tables[0].Rows[0]["report"].ToString();
  DateTime st = Convert.ToDateTime(getTINFO.Tables[0].Rows[0]["stime"]);
  DateTime et = Convert.ToDateTime(getTINFO.Tables[0].Rows[0]["etime"]);
  Maticsoft.OAchargeReport getValueInfo = new Maticsoft.OAchargeReport();
  DataSet getValueInfoDS = getValueInfo.GetList("reportid=" + reportid + " and sendtime between '" + st + "' and '" + et + "'");

  GridView1.DataSource = getValueInfoDS;
  GridView1.DataBind();

  Response.Clear();
  Response.Buffer = true;
  Response.Charset = "utf-8";　　//("GB2312");为简体中文
  Response.AppendHeader("Content-Disposition", "attachment;filename=" + reportTile + ".xls");
  Response.ContentEncoding = System.Text.Encoding.GetEncoding("utf-8");　//GB231
  Response.ContentType = "application/ms-excel";
  this.EnableViewState = false;
  System.IO.StringWriter oStringWriter = new System.IO.StringWriter();
  System.Web.UI.HtmlTextWriter oHtmlTextWriter = new System.Web.UI.HtmlTextWriter(oStringWriter);
  StringWriter sw = new StringWriter();
  HtmlTextWriter htw = new HtmlTextWriter(sw);
  GridView1.RenderControl(htw);
  Response.Write(sw.ToString());
  //Response.End();
  }
  }
  catch
  {
  Response.Write("页面错误");
  }
  }
  }
  public override void VerifyRenderingInServerForm(Control control){}

}


------解决方案--------------------
先绑定数据到gridview,在导出
或使用模板
string fileName = "";
string filePath = Server.MapPath("");//路径
FileInfo fileInfo = new FileInfo(filePa