使用FileResult导出txtl数据文件

public FileResult ExportMobileNoTxt(SearchClientModel model)
{
            var sbTxt = new StringBuilder();

            for (int i = ; i < datalist.Count; i++)
            {
                sbTxt.Append(datalist[i].Mobile +"\r\n");
            }

            byte[] fileContents = Encoding.Default.GetBytes(sbTxt.ToString());
            return File(fileContents, "application/ms-txt", "MobileList.txt");
}