How to export a Repeater having linkbutton to excel?

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ASP.NET

I am having a repeater in which i used one column as linkbutton.i used ballon popup extender also in the same repeater. when i am trying to export the repeater to excel i am getting the following error,

"Control 'gdvDataQualityReport_ctl01_BalloonPopupExtender1' of type 'BalloonPopupExtender' must be placed inside a form tag with runat=server."

gdvDataQualityReport is my Repeater name and BalloonPopupExtender1 is my balloonpopupextender name.

i used the following code for exporting data in repeater,

Response.Clear();
            Response.Buffer = true;
            Response.AddHeader("content-disposition","attachment;filename=DataAvailability.xls");
            Response.Charset = "";
            Response.ContentType = "application/vnd.ms-excel";
            System.IO.StringWriter stringWrite = new System.IO.StringWriter();
            System.Web.UI.HtmlTextWriter htmlWrite = new HtmlTextWriter(stringWrite);
            gdvDataQualityReport.RenderControl(htmlWrite);
            gdvDataQualityReport.RenderControl(htmlWrite);
            Response.Write("<table>");
            Response.Write(stringWrite.ToString());
            Response.Write("</table>");
            Response.End(); 

Can anyone please help me in solving this?