使用WebClient后的Response编码的问题

使用WebClient可以抓取别的网页的内容,然后提供下载,但是使用Response输出时要注意编码问题,否则打开是一片空白。使如：

        protected override void Render(HtmlTextWriter writer)
        {
            string url = string.Format("{0}/con001_projectmanage/job/downloadresume.aspx?resumeid={1}",
                Request.Url.AbsoluteUri.Replace(Request.Url.PathAndQuery,string.Empty).TrimEnd('/').ToLower(),
                Request.QueryString["resumeid"]);

            WebClient wb = new WebClient();
            byte[] buf = wb.DownloadData(url);//从指定的Uri获取数据
            
            Page.Response.Clear();
            Response.Charset = "UTF-8";        //TODO:指定的Charset要与ContentEncoding相一致。
            Page.Response.ContentType = "text/html";
            Page.Response.AddHeader("content-disposition", "attachment; filename=\"resume.htm\""); 
            Page.Response.ContentEncoding = Encoding.UTF8;
            Page.Response.OutputStream.Write(buf, 0, buf.Length);
            Page.Response.Flush();
            Page.Response.End();
        }