Export GridView into Excel

below i am describing how to export a grid data..

    /// pass gridveiw into this funtion  
    private void ExportGridView(GridView gv)
    {
        string attachment = "attachment; filename=ArchiveOrderList.xls"; //name of excel filename         
        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();
        //gvOrderInfo.Parent.Controls.Add(frm);         
        //gvOrderInfo.Parent.Controls.Add(frm);         
        this.Controls.Add(frm);
        frm.Attributes["runat"] = "server";
        frm.Controls.Add(gv);
        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);
            }
            else if (gv.Controls[i].GetType() == typeof(ImageButton))
            {
                continue;
            }
            if (gv.Controls[i].HasControls())
            {
                PrepareGridViewForExport(gv.Controls[i]);
            }
        }
    }

    public override void VerifyRenderingInServerForm(Control control)
    {
        if (control.ID == GridView1.Id) // here GridView1 is the id of gridview of page
        {
            //Doing nothing             
            return;
        }
        base.VerifyRenderingInServerForm(control);
    }