导出excel的奇怪问题

从网上考了一段datagrid导出excel的代码,自己修改了一下,可是遇到个奇怪的问题,在datagrid里的数据少于10行时,导出的excel文件会是乱码,大于10行一切正常! 希望有达人可以指点一下!

private void Button1_Click(object sender, System.EventArgs e)
  {
   try
   {
    Response.Clear(); 
    Response.Buffer= true; 
    Response.Charset="GB2312";    
    string strFileTitle = HttpUtility.UrlEncode(Request.QueryString["reportName"]);
    Response.AppendHeader("Content-Disposition","attachment;filename="+strFileTitle+".xls");    
    Response.ContentEncoding=System.Text.Encoding.UTF8;
    Response.ContentType = "application/ms-excel";
    this.EnableViewState = false;
    System.Globalization.CultureInfo myCItrad = new System.Globalization.CultureInfo("ZH-CN",true);
    //define a io 
    System.IO.StringWriter oStringWriter = new System.IO.StringWriter(myCItrad); 
    System.Web.UI.HtmlTextWriter oHtmlTextWriter = new System.Web.UI.HtmlTextWriter(oStringWriter);
    this.DataGrid2.RenderControl(oHtmlTextWriter); 
    Response.Write(oStringWriter.ToString());
    Response.End();
   }
   catch(Exception er)
   {
    string aa= er.ToString();
    aa +="";
   }
  }