public FileResult ExportMobileNoTxt(SearchClientModel model)
{
            var sbTxt = new StringBuilder();            for (int i = 0; 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");
}