Export Gridview

Code:

        protected void OnClick_lbtnBack(object sender, EventArgs e)
        {
            string requestPage = Session["CAABackToPreviousPage"].ToString();
            Response.Redirect(requestPage, true);
        }

        protected void OnClick_btnExport(object sender, EventArgs e)
        {
            //Export the GridView to Excel
            //PrepareGridViewForExport(GridView1);
            ExportGridView();
        }

        private void ExportGridView()
        {
            Response.Clear();
            Response.Buffer = true;
            Response.AddHeader("content-disposition", "attachment;filename=ContestWinnerReport.csv");
            Response.Charset = "";
            Response.ContentType = "application/text";

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

            StringBuilder sb = new StringBuilder();
            for (int k = 0; k < GridView1.Columns.Count; k++)
            {
                //add separator
                sb.Append(GridView1.Columns[k].HeaderText + ',');
            }
            //append new line
            sb.Append("\r\n");
            int testint = GridView1.Rows.Count;
            for (int i = 0; i < GridView1.Rows.Count; i++)
            {
                for (int k = 0; k < GridView1.Columns.Count; k++)
                {
                    //add separator
                    if (k == 2)
                        sb.Append("'" + GridView1.Rows[i].Cells[k].Text + ',');
                    else
                        sb.Append(GridView1.Rows[i].Cells[k].Text + ',');
                }
                //append new line
                sb.Append("\r\n");
            }
            Response.Output.Write(sb.ToString());
            Response.Flush();
            Response.End();

            ////GridView1.DataSource = Cache["ContestList"];
            ////GridView1.DataBind();
            //GridView1.HeaderStyle.ForeColor = System.Drawing.Color.Black;
            //string attachment = "attachment; filename=ContestWinnerReport.xls";
            //Response.ClearContent();
            //Response.AddHeader("content-disposition", attachment);
            //Response.ContentType = "application/ms-excel";
            ////Response.ContentType = "application/text";
            //StringWriter sw = new StringWriter();
            //HtmlTextWriter htw = new HtmlTextWriter(sw);
            //GridView1.RenderControl(htw);
            //Response.Write(sw.ToString());
            //Response.End();

            //string attachment = "attachment; filename=Contacts.xls";
            //Response.ClearContent();
            //Response.AddHeader("content-disposition", attachment);
            //Response.ContentType = "application/ms-excel";
            //StringWriter sw = new StringWriter();
            //HtmlTextWriter htw = new HtmlTextWriter(sw);

            //// Create a form to contain the grid
            //HtmlForm frm = new HtmlForm();
            //GridView1.Parent.Controls.Add(frm);
            //frm.Attributes["runat"] = "server";
            //frm.Controls.Add(GridView1);

            //frm.RenderControl(htw);
            ////GridView1.RenderControl(htw);
            //Response.Write(sw.ToString());
            //Response.End();
        }

        private void PrepareGridViewForExport(Control gv)
        {
            LinkButton lb = new LinkButton();
            Literal l = new Literal();
            string name = String.Empty;
            for (int i = 0; i < gv.Controls.Count; i++)
            {
                if (gv.Controls[i].GetType() == typeof(LinkButton))
                {
                    l.Text = (gv.Controls[i] as LinkButton).Text;
                    gv.Controls.Remove(gv.Controls[i]);
                    gv.Controls.AddAt(i, l);
                }
                else if (gv.Controls[i].GetType() == typeof(DropDownList))
                {
                    l.Text = (gv.Controls[i] as DropDownList).SelectedItem.Text;
                    gv.Controls.Remove(gv.Controls[i]);
                    gv.Controls.AddAt(i, l);
                }
                else if (gv.Controls[i].GetType() == typeof(CheckBox))
                {
                    l.Text = (gv.Controls[i] as CheckBox).Checked ? "True" : "False";
                    gv.Controls.Remove(gv.Controls[i]);
                    gv.Controls.AddAt(i, l);
                }
                if (gv.Controls[i].HasControls())
                {
                    PrepareGridViewForExport(gv.Controls[i]);
                }
            }
        }