web开发下的各种下载方法

利用TransmitFile方法，解决Response.BinaryWrite下载超过400mb的文件时导致Aspnet_wp.exe进程回收而无法成功下载的问题。 代码如下：

 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实现下载

 string fileName ="aaa.zip";//客户端保存的文件名

  string filePath=Server.MapPath("DownLoad/aaa.zip");//路径



  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分块下载

string fileName = "aaa.zip";//客户端保存的文件名

  string filePath = Server.MapPath("DownLoad/aaa.zip");//路径



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



  if (fileInfo.Exists == true)

  {

  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

  byte[] buffer = new byte[ChunkSize];



  Response.Clear();

  System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);

  long dataLengthToRead = iStream.Length;//获取下载的文件总大小

  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));//读取的大小

  Response.OutputStream.Write(buffer, 0, lengthRead);

  Response.Flush();

  dataLengthToRead = dataLengthToRead - lengthRead;

  }

  Response.Close();

  }

  //流方式下载

 string fileName = "aaa.zip";//客户端保存的文件名

  string filePath = Server.MapPath("DownLoad/aaa.zip");//路径



  //以字符流的形式下载文件

  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";

  //通知浏览器下载文件而不是打开

  Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));

  Response.BinaryWrite(bytes);

  Response.Flush();

  Response.End();

最后一种支持断点下载

/// <summary>

        /// 支持断点续传的下载大文件的函数

        /// </summary>

        /// <param name="downloadFilePath">被下载文件的路径，相对和绝对都可以</param>

        /// <param name="showFileName">显示给用户的文件名，可以为空</param>

        /// <param name="fileType">要下载的文件类型，如果不确定，请留空</param>

        /// <remarks>用于大文件的下载</remarks>

        public static void BigFileDownload(string downloadFilePath, string showFileName, string fileType)

        {

            downloadFilePath = downloadFilePath.Trim();

            if(string.Empty == downloadFilePath)

                ShowErrorMessage("没有指定要下载的文件路径！");

            

            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;

                    

                    输出HTTP头信息

                    

                    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);

            }

            // 结束文件下载，此句不可缺少，否则会把本页的HTML代码一起下载文件里

            HttpContext.Current.Response.End();

        }



        /// <summary>

        /// 输出错误信息给用户，采用客户端弹出框的方式

        /// </summary>

        /// <param name="errorMessage">错误信息的内容</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();

        }