web開發下的各種下載方法

利用TransmitFile方法，解決Response.BinaryWrite下載超過400mb的文件時導致Aspnet_wp.exe進程回收而無法成功下載的問題。 代碼如下：

 Response.ContentType = "application/x-zip-compressed";
  Response.AddHeader("Content-Disposition", "attachment;filename=z.zip");
  string filename = Server.MapPath("DownLoad/aaa.zip");
  Response.TransmitFile(filename);

IO的WriteFile實現下載

 string fileName ="aaa.zip";//客戶端保存的文件名
  string filePath=Server.MapPath("DownLoad/aaa.zip");//路徑

  FileInfo fileInfo = new FileInfo(filePath);
  Response.Clear();
  Response.ClearContent();
  Response.ClearHeaders();
  Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
  Response.AddHeader("Content-Length", fileInfo.Length.ToString());
  Response.AddHeader("Content-Transfer-Encoding", "binary");
  Response.ContentType = "application/octet-stream";
  Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
  Response.WriteFile(fileInfo.FullName);
  Response.Flush();
  Response.End();

WriteFile分塊下載

string fileName = "aaa.zip";//客戶端保存的文件名
  string filePath = Server.MapPath("DownLoad/aaa.zip");//路徑

  System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);

  if (fileInfo.Exists == true)
  {
  const long ChunkSize = 102400;//100K 每次讀取文件，只讀取100Ｋ，這樣可以緩解服務器的壓力
  byte[] buffer = new byte[ChunkSize];

  Response.Clear();
  System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);
  long dataLengthToRead = iStream.Length;//獲取下載的文件總大小
  Response.ContentType = "application/octet-stream";
  Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));
  while (dataLengthToRead > 0 && Response.IsClientConnected) 
  {
  int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//讀取的大小
  Response.OutputStream.Write(buffer, 0, lengthRead);
  Response.Flush();
  dataLengthToRead = dataLengthToRead - lengthRead;
  }
  Response.Close();
  }

  //流方式下載

 string fileName = "aaa.zip";//客戶端保存的文件名
  string filePath = Server.MapPath("DownLoad/aaa.zip");//路徑

  //以字符流的形式下載文件
  FileStream fs = new FileStream(filePath, FileMode.Open);
  byte[] bytes = new byte[(int)fs.Length];
  fs.Read(bytes, 0, bytes.Length);
  fs.Close();
  Response.ContentType = "application/octet-stream";
  //通知瀏覽器下載文件而不是打開
  Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
  Response.BinaryWrite(bytes);
  Response.Flush();
  Response.End();

最后一種支持斷點下載

/// <summary>
        /// 支持斷點續傳的下載大文件的函數
        /// </summary>
        /// <param name="downloadFilePath">被下載文件的路徑，相對和絕對都可以</param>
        /// <param name="showFileName">顯示給用戶的文件名，可以為空</param>
        /// <param name="fileType">要下載的文件類型，如果不確定，請留空</param>
        /// <remarks>用於大文件的下載</remarks>
        public static void BigFileDownload(string downloadFilePath, string showFileName, string fileType)
        {
            downloadFilePath = downloadFilePath.Trim();
            if(string.Empty == downloadFilePath)
                ShowErrorMessage("沒有指定要下載的文件路徑！");
            
            if(downloadFilePath.IndexOf(":") < 0)
                downloadFilePath = System.Web.HttpContext.Current.Server.MapPath(downloadFilePath);

            showFileName = showFileName.Trim();
            if(string.Empty == showFileName)
                showFileName = Path.GetFileName(downloadFilePath);

            showFileName = System.Web.HttpUtility.UrlEncode(System.Web.HttpContext.Current.Request.ContentEncoding.GetBytes(showFileName));
            
            fileType = fileType.Trim();
            if(string.Empty == fileType)
                fileType = "application/octet-stream";

            System.Web.HttpContext.Current.Response.Clear();
            Stream objStream = null;
            byte[] btBuffer = new byte[8192];  // 1024*8 = 8Kb
            int intLength = 0;
            long lngData2Read = 0;
            try
            {
                using(objStream = new FileStream(downloadFilePath, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    lngData2Read = objStream.Length;
                    
                    輸出HTTP頭信息
                    
                    while(lngData2Read > 0)
                    {
                        if(HttpContext.Current.Response.IsClientConnected)
                        {
                            intLength = objStream.Read(btBuffer, 0, 8192);
                            HttpContext.Current.Response.OutputStream.Write(btBuffer, 0, intLength);
                            HttpContext.Current.Response.Flush();
                            lngData2Read -= intLength;
                            btBuffer = new byte[8192];
                        }
                        else
                        {
                            lngData2Read = -1;
                        }
                    }
                }
            }
            catch(Exception ex)
            {
                ShowErrorMessage(ex.Message);
            }
            // 結束文件下載，此句不可缺少，否則會把本頁的HTML代碼一起下載文件里
            HttpContext.Current.Response.End();
        }

        /// <summary>
        /// 輸出錯誤信息給用戶，采用客戶端彈出框的方式
        /// </summary>
        /// <param name="errorMessage">錯誤信息的內容</param>
        internal static void ShowErrorMessage(string errorMessage)
        {
            errorMessage = errorMessage.Replace("'", "\"");
            System.Web.HttpContext.Current.Response.Write("<script language='javascript'>");
            System.Web.HttpContext.Current.Response.Write("alert('");
            System.Web.HttpContext.Current.Response.Write(errorMessage);
            System.Web.HttpContext.Current.Response.Write("');</script>");
            System.Web.HttpContext.Current.Response.End();
        }