nl.fileid = Int32.Parse(id);  //服务器上对应的id
            Stream stream = Lawsuit.DownLoad(nl);//服务器上的Stream 数据

            Response.Buffer = false;
            Response.AddHeader("Connection", "Keep-Alive");
            Response.ContentType = "application/octet-stream";
            Response.AddHeader("Content-Disposition", "attachment;filename=" + url); // 此处文件名如果是中文在浏览器默认是筹码,应该加HttpUtility.UrlEncode(filename)   url：为下载文件的服务器地址和名称

            while (true)    //如果文件大于缓冲区，通过while循环多次加载文件 
            {
                //开辟缓冲区空间   
                byte[] buffer = new byte[1024];  //读取文件的数据   
                int leng = stream.Read(buffer, 0, 1024);
                if (leng == 0)             //到文件尾，结束   
                    break;
                if (leng == 1024)            //读出的文件数据长度等于缓冲区长度，直接将缓冲区数据写入  
                    Response.BinaryWrite(buffer);           //向客户端发送数据流 
                else
                {
                    //读出文件数据比缓冲区小，重新定义缓冲区大小，只用于读取文件的最后一个数据块  
                    byte[] b = new byte[leng]; for (int i = 0; i < leng; i++)
                        b[i] = buffer[i];
                    Response.BinaryWrite(b);
                }
            }
            stream.Close();//关闭下载文件  
            Response.End();//结束文件下载 

 1         /// <summary>
 2         /// 根据流创建pdf
 3         /// </summary>
 4         /// <param name="_Stream"></param>
 5         /// <returns></returns>
 6         public string CreateCasePDF(Stream _Stream)
 7         {
 8             string pdfUrl = Server.MapPath("../Content/FilePdf");//pdf保存地址
 9             if (Directory.Exists(pdfUrl) == false)//如果不存在就创建PDFFile文件夹
10             {
11                 Directory.CreateDirectory(pdfUrl);
12             }
13             DocClient proxy = new DocClient();
14             try
15             {
16                 string guid = Guid.NewGuid().ToString();
17                 FileInfo file = new FileInfo(pdfUrl + guid + ".pdf");
18                 Stream write = file.OpenWrite();
19                 write.Position = long.Parse("0");
20                 byte[] buf = new byte[1024 * 2048];
21                 int size = -1;
22                 long sum = long.Parse("0");
23                 while ((size = _Stream.Read(buf, 0, buf.Length)) > 0)
24                 {
25                     write.Write(buf, 0, size);
26                     sum += size;
27                 }
28                 write.Close();
29                 _Stream.Close();
30                 return guid;
31             }
32             catch (Exception)
33             {
34                 return null;
35             }
36         }

        /// <summary>
        /// 获取文件的MD5值
        /// </summary>
        /// <param name="stream"></param>
        /// <returns></returns>
        public static string GetMD5HashFromStream(Stream stream)
        {
            try
            {
                System.Security.Cryptography.MD5CryptoServiceProvider md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
                byte[] data = md5.ComputeHash(stream);
                StringBuilder sBuilder = new StringBuilder();
                for (int i = 0; i < data.Length; i++)
                {
                    sBuilder.Append(data[i].ToString("x2"));
                }
                return sBuilder.ToString().ToUpper();
            }
            catch (Exception ex)
            {
                throw new Exception("GetMD5HashFromFile() fail,error:" + ex.Message);
            }
        }

                string path = Server.MapPath("../Content/FilePdf");// 删除指定文件下的文件夹及其文件
                Directory.Delete(path, true);
                Directory.CreateDirectory(path);