how to extract data from database to an excell file and generate graph

public static void ExportXls(GridView gridName, string filename)
    {
        HttpContext.Current.Response.Clear();
        HttpContext.Current.Response.AddHeader("content-disposition", "attachment;filename=" + filename + ".xls");
        HttpContext.Current.Response.Charset = "";
        HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);
        HttpContext.Current.Response.ContentType = "application/Excel";
        System.IO.StringWriter stringWrite = new System.IO.StringWriter();
        System.Web.UI.HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);
        gridName.RenderControl(htmlWrite);
        HttpContext.Current.Response.Write(stringWrite.ToString());
        HttpContext.Current.Response.End();
    }

public override void VerifyRenderingInServerForm(Control control)
    {
 
    }