public void DownFile(string url)
        {
            if (string.IsNullOrEmpty(url)) return;
            try
            {
                WebClient UrlFile = new WebClient();

                HttpContext.Current.Response.Clear();
                HttpContext.Current.Response.ClearHeaders();
                HttpContext.Current.Response.BufferOutput = false;
                HttpContext.Current.Response.ContentType = "application/octet-stream";
                HttpContext.Current.Response.AppendHeader("Content-disposition", "attachment;filename=" + HttpUtility.UrlEncode(FileName, System.Text.Encoding.UTF8));
                byte[] b = UrlFile.DownloadData(url);
                HttpContext.Current.Response.BinaryWrite(b);
                HttpContext.Current.Response.Flush();
                HttpContext.Current.Response.End();
            }
            catch
            { }
        }