方式一：

public FileStreamResult DownFile(string filePath, string fileName)          {              string absoluFilePath = Server.MapPath(System.Configuration.ConfigurationManager.AppSettings["AttachmentPath"] + filePath);              return File(new FileStream(absoluFilePath, FileMode.Open), "application/octet-stream", Server.UrlEncode(fileName));          }

方式二：

public ActionResult DownFile(string filePath, string fileName)          {              filePath = Server.MapPath(System.Configuration.ConfigurationManager.AppSettings["AttachmentPath"] + filePath);              FileStream fs = new FileStream(filePath, FileMode.Open);              byte[] bytes = new byte[(int)fs.Length];              fs.Read(bytes, 0, bytes.Length);              fs.Close();              Response.Charset = "UTF-8";              Response.ContentEncoding = System.Text.Encoding.GetEncoding("UTF-8");              Response.ContentType = "application/octet-stream";                Response.AddHeader("Content-Disposition", "attachment; filename=" + Server.UrlEncode(fileName));              Response.BinaryWrite(bytes);              Response.Flush();              Response.End();              return new EmptyResult();            }