Export Data To Excel In C#

protected void btnExport_Click(object sender, EventArgs e)
{
    ExportGridToExcel();
}
private void ExportGridToExcel()
{
    try
    {
        con.Open();
        SqlCommand com;
        SqlDataAdapter ad;
        com = new SqlCommand("select fname as FirstName,email as EmailId,contact as ContactNo,nopax as NoPax,hotelcate as HotelCategory,country as Country,convert(varchar,traveldate,103) as TravelDate,custdetail as CustomizeDetails,status as Status,enqdate as EnquiryDate from customize", con);
        ad = new SqlDataAdapter();
        ad.SelectCommand = com;
        DataTable dt = new DataTable();
        ad.Fill(dt);
        GridView gd = new GridView();
        gd.DataSource = dt;
        gd.DataBind();
        Response.Clear();
        Response.AddHeader("content-disposition", "attachment;filename=Branch.xls");
        Response.ContentType = "application/ms-excel";
        string k = GetGridViewHtml(gd);
        Response.Write(k);
        Response.End();
    }
    catch (Exception ex)
    {
        throw ex;
    }
    finally
    {
        con.Close();
    }
}
public string GetGridViewHtml(Control c)
{
    System.IO.StringWriter sw = new System.IO.StringWriter();
    HtmlTextWriter hw = new HtmlTextWriter(sw);
    c.RenderControl(hw);
    return sw.ToString();
}