GridView导出Excel数据为空

GridView导出Excel数据为空，紧急求助
代码如下：

C# code

…………………………public void ExportToExcel(Control ctrl, String FileName)    {        GridView gv = (GridView)ctrl;        gv.AllowPaging = false;//清除分页         gv.AllowSorting = false;// 清除排序        GetExcel();        HttpContext.Current.Response.Charset = "GB2312";        HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.GetEncoding("GB2312");        HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=" + FileName);        HttpContext.Current.Response.ContentType = "application/ms-excel";        HttpContext.Current.Response.Write(AddExcelHead());        StringWriter tw = new StringWriter();        HtmlTextWriter hw = new HtmlTextWriter(tw);        gv.RenderControl(hw);        HttpContext.Current.Response.Write(tw.ToString());        HttpContext.Current.Response.Write(AddExcelbottom());//网格        HttpContext.Current.Response.End();        gv.AllowSorting = true; //恢复分页         gv.AllowPaging = true; //恢复排序         GetData2();    }public void GetExcel()    {        GridView2.DataSource = B_FileInfo1.GetExcle("'%,'+'" + Session["Townid"].ToString() + "'+',%' and b.townid='" + Session["Townid"].ToString() + "'" + " and FdataTime between '" + before.Value + "' and '" + later.Value + "'");        GridView2.DataBind();    }private void GetData2()    {        GridView2.DataSource = B_FileInfo1.GetExcle("'%,'+'" + Session["Townid"].ToString() + "'+',%' and b.townid='" + Session["Townid"].ToString() + "'" + " and FdataTime between '" + before.Value + "' and '" + later.Value + "'");        GridView2.DataBind();    }……………………………………public override void VerifyRenderingInServerForm(Control control)    {    }

C# code

public override void VerifyRenderingInServerForm(Control control)    {    }