.net文件上传、下载

/// <summary>
        /// 上传文件
        /// </summary>
        /// <returns></returns>
        [HttpPost]
        public ActionResult Upload()
        {
            //调用页面的上传控件，实现文件的上传
            var file = Request.Files[0];
            var id = Request["id"] ?? ""; //如果是重新上传的话，会有id
            var type = Request["type"] ?? ""; //主文件没有type，照片卷的照片标签、图纸卷的图纸备考表、拓片及摹本的登记表、电子文件卷的光盘标签，这几类辅助文件会有type
            if ((file != null) && (file.ContentLength > 0))
            {
                string uploadfilename = file.FileName; //用户上传的原始文件名，数据库中也要存储，用于用户下载的时候重命名
                string extention = uploadfilename.Substring(uploadfilename.LastIndexOf(".")).ToLower();
                string saveFileName = DateTime.Now.ToString("yyyyMMddHHmmssfff") + extention;
                string path = Server.MapPath("~/Upload/SYZL/Doc/");//取得上传的目标文件夹
                string filePath = path + saveFileName;
                if (!Directory.Exists(path))
                {
                    Directory.CreateDirectory(path);
                }
                file.SaveAs(Path.Combine(path, saveFileName));  //上传文件
                if ((extention == ".pdf") || (extention == ".doc") || (extention == ".docx") || (extention == ".xls") || (extention == ".xlsx") || (extention == ".ppt") || (extention == ".pptx"))
                {
                    //在完成pdf,office格式文档上传之后，进行文档格式的转换，以便使用flexpaper在线预览 
                    ConvertFileFormat(saveFileName);
                    /*
                    var workingThread = new Thread(ConvertFileFormat);
                    workingThread.Start(saveFileName);
                     */
                }
                //更新数据库记录，新增数据库记录的操作不在这里做，在提交表单的时候做，原始文件名和保存文件名已经返回给表单
                if (id != "") //id不为空，是重新上传文件动作，需要更新主键为id的数据库记录
                {
                    var syxxxq = db.T_SYXXXQ.Find(Int32.Parse(id));
                    if (syxxxq != null)
                    {
                        //判断type是否为空，如果type为空，则为主文件，否则，则为辅文件
                        if (type != "")
                        {
                            var ajdhqlw = syxxxq.SYXXZLLXBH.Trim(); //案卷档号前两位
                            //如果老文件存在，则删除老文件
                            DeleteOldFile(syxxxq.LJWJMC);
                            //更新图纸卷的"图纸备考表原始上传文件名":TZBKBYSM，"图纸备考表保存文件名":TZBKBBCM
                            syxxxq.NRBT = uploadfilename; //原始文件名
                            syxxxq.LJWJMC = saveFileName;   //保存文件名
                            db.Entry(syxxxq).State = EntityState.Modified;
                            db.SaveChanges();
                        }
                        else
                        {
                            //如果老文件存在，则删除老文件
                            DeleteOldFile(syxxxq.NRBT);
                            //上传的是主文件,更新主文件数据库记录
                            syxxxq.NRBT = uploadfilename; //原始文件名
                            syxxxq.LJWJMC = saveFileName;   //保存文件名
                            syxxxq.WJLX = GetFileTypeByExtention(extention);
                            syxxxq.ADDSJ = DateTime.Now;
                            db.Entry(syxxxq).State = EntityState.Modified;
                            db.SaveChanges();
                        }
                    }
                }
                //返回保存文件名，原始文件名
                return Content("{\"NRBT\":\"" + uploadfilename + "\",\"LJWJMC\":\"" + saveFileName + "\",\"WJLJ\":\"" + filePath + "\",\"WJLX\":\"" + GetFileTypeByExtention(extention) + "\"}");
            }
            return Content("0");
        }

 1 public string downloadFile()
 2         {
 3             string id = Request["id"] ?? "";
 4             if (!string.IsNullOrEmpty(id))
 5             {
 6                 var syxxxq = db.T_SYXXXQ.Find(Int32.Parse(id));
 7                 string path = Server.MapPath("~/Upload/SYZL/Doc/");//取得上传的目标文件夹
 8                 string fileName = syxxxq.LJWJMC;//保存的路径文件名
 9                 string khdFileName = syxxxq.NRBT;//客户端文件名
10                 string filePath = path + fileName;//服务器上保存的路径
11                 var fileInfo = new FileInfo(filePath);
12                 if (fileInfo.Exists == true)
13                 {
14                     #region 未测试的另一种下载方法
15                     //FileInfo fi = new FileInfo(fileName);
16                     //Response.Clear();
17                     //Response.ClearHeaders();
18                     //Response.Buffer = true;
19                     //Response.Charset = "GB2312";
20 
21                     ////添加头信息，为 "文件下载/另存为 "对话框指定默认文件名 
22                     //Response.AppendHeader("Content-Disposition", "attachment;filename="
23                     //    + HttpUtility.UrlEncode(Path.GetFileName(filePath),
24                     //    System.Text.Encoding.UTF8));
25                     //Response.AppendHeader("Content-Length", fi.Length.ToString());
26                     //Response.ContentType = "application/octet-stream";
27                     //Response.Filter.Close();
28                     //Response.WriteFile(filePath);
29                     //Response.Flush();
30                     //Response.End(); 
31                     #endregion
32                     const long ChunkSize = 102400;//100K 每次读取文件，只读取100K，这样可以缓解服务器的压力
33                     byte[] buffer = new byte[ChunkSize];
34 
35                     Response.Clear();
36                     var iStream = System.IO.File.OpenRead(filePath);
37                     long dataLengthToRead = iStream.Length;//获取下载的文件总大小
38                     Response.ContentType = "application/octet-stream";
39                     Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));
40                     while (dataLengthToRead > 0 && Response.IsClientConnected)
41                     {
42                         int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//读取的大小
43                         Response.OutputStream.Write(buffer, 0, lengthRead);
44                         Response.Flush();
45                         dataLengthToRead = dataLengthToRead - lengthRead;
46                     }
47                     Response.Close();
48                 }
49             }
50             return "下载的文件不存在!";
51         }