asp.net convert panel data and gridview data to word.doc

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ASP.NET

Response.AddHeader("content-disposition", "attachment;filename=Export.doc");
        Response.Cache.SetCacheability(HttpCacheability.NoCache);
        Response.ContentType = "application/vnd.word";

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


        System.Web.UI.HtmlControls.HtmlForm frm = new System.Web.UI.HtmlControls.HtmlForm();
        pnlPerson.Parent.Controls.Add(frm);
        GridView1.Parent.Controls.Add(frm);
       
        frm.Attributes["runat"] = "server";
        frm.Controls.Add(pnlPerson);
        frm.Controls.Add(GridView1);
        
        frm.RenderControl(htmlWrite);
        // frm.RenderControl(strBody);


        Response.Write(stringWrite.ToString());
       
        Response.End();

but i getting error while add panel data that have calender function
error-Extender control 'CalendarExtender1' is not a registered extender control. Extender controls must be registered using RegisterExtenderControl() before calling RegisterScriptDescriptors().
Parameter name: extenderControl