以流的方式下載檔案——問題

  請問誰知道這個是什麼錯誤昂？以流的方式下載檔案

               int fileid = Convert.ToInt32(e.CommandArgument.ToString());
                DataSet ds = tenantfileBll.GetFileName(fileid, CurrentUser.TenantID);
                string fileName = ds.Tables[0].Rows[0]["FileName"].ToString();//1 用戶端儲存的檔案名稱
                //2 找到檔案的路徑
                string filePath = Server.MapPath("files/" + CurrentUser.TenantID + "/" + fileName);//路徑
                //3 以字元流的形式下載檔案 
                FileStream fs = new FileStream(filePath, FileMode.Open);
                byte[] bytes = new byte[(int)fs.Length];
                fs.Read(bytes, 0, bytes.Length);
                fs.Close();
                Response.ContentType = "application/octet-stream";
                Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
                Response.BinaryWrite(bytes);
                Response.Flush();
                Response.End();