var stream = new MemoryStream();            var writer = new StreamWriter(stream);            //写入你的文件内容，我这里是一个字符串            writer.Write(sql);            writer.Flush();            stream.Position = 0;            //设定文件类型            var actionresult = new FileStreamResult(stream, new Microsoft.Net.Http.Headers.MediaTypeHeaderValue("text/txt"));            //设定文件名称            actionresult.FileDownloadName = "CreateTableSql.txt";            return actionresult;