页面导出为word内容是空的

Question

HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=xx.doc");
            HttpContext.Current.Response.Charset = "UTF-8";
            HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.Default;
            HttpContext.Current.Response.ContentType = "application/ms-word   ";
            Page.EnableViewState = false;
            System.IO.StringWriter tw = new System.IO.StringWriter();
            System.Web.UI.HtmlTextWriter hw = new System.Web.UI.HtmlTextWriter(tw);
            //this.Page.RenderControl(hw);
            HttpContext.Current.Response.Write(tw.ToString());
            HttpContext.Current.Response.End();     
能导出word但内容是空的，什么问题，哪位大侠做过？