• using

  System;
  using

  System.Data;
  using

  System.Configuration;
  using

  System.Web;
  using

  System.Web.Security;
  using

  System.Web.UI;
  using

  System.Web.UI.WebControls;
  using

  System.Web.UI.WebControls.WebParts;
  using

  System.Web.UI.HtmlControls;
  using

  System.IO;
   
  public

  partial

  class

  _Default : System.Web.UI.Page
  {
  protected

  void

  Page_Load(

  object

  sender, EventArgs e)
  {
   
  }
   
  //TransmitFile实现下载
  protected

  void

  Button1_Click(

  object

  sender, EventArgs e)
  {
  Response.ContentType =

  "application/x-zip-compressed"

  ;
  Response.AddHeader(

  "Content-Disposition"

  ,

  "attachment;filename=z.zip"

  );
  string

  filename = Server.MapPath(

  "DownLoad/z.zip"

  );
  Response.TransmitFile(filename);
  }
   
  //WriteFile实现下载
  protected

  void

  Button2_Click(

  object

  sender, EventArgs e)
  {
  string

  fileName =

  "asd.txt"

  ;

  //客户端保存的文件名
  string

  filePath=Server.MapPath(

  "DownLoad/aaa.txt"

  );

  //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
  protected

  void

  Button3_Click(

  object

  sender, EventArgs e)
  {
  string

  fileName =

  "aaa.txt"

  ;

  //客户端保存的文件名
  string

  filePath = Server.MapPath(

  "DownLoad/aaa.txt"

  );

  //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
  protected

  void

  Button4_Click(

  object

  sender, EventArgs e)
  {
  string

  fileName =

  "aaa.txt"

  ;

  //客户端保存的文件名
  string

  filePath = Server.MapPath(

  "DownLoad/aaa.txt"

  );

  //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();
   
  }
  }

转自：