i want to export data from gridview to excel

This is button click code...myDataGrid is datagrid name  

protected void btnExcel_Click1(object sender, EventArgs e)

    {

        Response.Clear();

        Response.AddHeader("content-disposition", "attachment;filename=FileName.xls");

        Response.Charset = "";

        Response.Cache.SetCacheability(HttpCacheability.NoCache);

        Response.ContentType = "application/vnd.xls";

        System.IO.StringWriter stringWrite = new System.IO.StringWriter();

        System.Web.UI.HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);

        myDataGrid.RenderControl(htmlWrite);

        Response.Write(stringWrite.ToString());

        Response.End();

    }