public static void ExportToExcelMethodTwo(string strFileName, GridView gv)
        {
            System.Text.StringBuilder sb  = new System.Text.StringBuilder();
            System.IO.StringWriter    sw  = new System.IO.StringWriter(sb);
            HtmlTextWriter            htw = new HtmlTextWriter(sw);

            Page     page = new Page();
            HtmlForm form = new HtmlForm();

            //GridView1.EnableViewState = false;
            //GridView1.AllowPaging = false;
            //gv.DataBind();

            page.EnableEventValidation = false;
            page.DesignerInitialize();
            page.Controls.Add(form);


            if (gv.HeaderRow != null)
            {
                GridViewExportUtil.PrepareControlForExport(gv.HeaderRow);
            }


            //  add each of the data rows to the table
            foreach (GridViewRow row in gv.Rows)
            {
                GridViewExportUtil.PrepareControlForExport(row);
            }

            //  add the footer row to the table
            if (gv.FooterRow != null)
            {
                GridViewExportUtil.PrepareControlForExport(gv.FooterRow);
            }

            form.Controls.Add(gv);
            page.RenderControl(htw);


            HttpContext.Current.Response.Clear();
            HttpContext.Current.Response.Buffer      = true;
            HttpContext.Current.Response.ContentType = "application/ms-excel";// vnd.ms-excel";
            HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=" + strFileName + ".xls");
            HttpContext.Current.Response.Charset = "UTF-8";

            HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);
            HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.Default;
            HttpContext.Current.Response.Write(sb.ToString());
            HttpContext.Current.Response.End();
        }
        /// <summary>
        ///
        /// </summary>
        /// <param name="fileName"></param>
        /// <param name="gv"></param>
        public static void Export(string fileName, GridView gv)
        {
            HttpContext.Current.Response.Clear();
            HttpContext.Current.Response.AddHeader(
                "content-disposition", string.Format("attachment; filename={0}", fileName));
            HttpContext.Current.Response.ContentType = "application/ms-excel";

            using (StringWriter sw = new StringWriter())
            {
                using (HtmlTextWriter htw = new HtmlTextWriter(sw))
                {
                    //  Create a form to contain the grid
                    Table table = new Table();

                    //  add the header row to the table
                    if (gv.HeaderRow != null)
                    {
                        GridViewExportUtil.PrepareControlForExport(gv.HeaderRow);
                        table.Rows.Add(gv.HeaderRow);
                    }

                    //  add each of the data rows to the table
                    foreach (GridViewRow row in gv.Rows)
                    {
                        GridViewExportUtil.PrepareControlForExport(row);
                        table.Rows.Add(row);
                    }

                    //  add the footer row to the table
                    if (gv.FooterRow != null)
                    {
                        GridViewExportUtil.PrepareControlForExport(gv.FooterRow);
                        table.Rows.Add(gv.FooterRow);
                    }

                    //  render the table into the htmlwriter
                    table.RenderControl(htw);

                    //  render the htmlwriter into the response
                    HttpContext.Current.Response.Write(sw.ToString());
                    HttpContext.Current.Response.End();
                }
            }
        }
        /// <summary>
        /// Replace any of the contained controls with literals
        /// </summary>
        /// <param name="control"></param>
        private static void PrepareControlForExport(Control control)
        {
            for (int i = 0; i < control.Controls.Count; i++)
            {
                Control current = control.Controls[i];
                if (current is LinkButton)
                {
                    control.Controls.Remove(current);
                    control.Controls.AddAt(i, new LiteralControl((current as LinkButton).Text));
                }
                else if (current is ImageButton)
                {
                    control.Controls.Remove(current);
                    control.Controls.AddAt(i, new LiteralControl((current as ImageButton).AlternateText));
                }
                else if (current is HyperLink)
                {
                    control.Controls.Remove(current);
                    control.Controls.AddAt(i, new LiteralControl((current as HyperLink).Text));
                }
                else if (current is DropDownList)
                {
                    control.Controls.Remove(current);
                    control.Controls.AddAt(i, new LiteralControl((current as DropDownList).SelectedItem.Text));
                }
                else if (current is CheckBox)
                {
                    control.Controls.Remove(current);
                    control.Controls.AddAt(i, new LiteralControl((current as CheckBox).Checked ? "Si" : "No"));
                }

                if (current.HasControls())
                {
                    GridViewExportUtil.PrepareControlForExport(current);
                }
            }
        }