文件下载 .net

protected void Button1_Click(object sender, EventArgs e)
  {

1. /*
2. 微软为Response对象提供了一个新的方法TransmitFile来解决使用Response.BinaryWrite
3. 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。
4. 代码如下：
5. */
6. Response.ContentType = "application/x-zip-compressed";
7. Response.AddHeader("Content-Disposition", "attachment;filename=z.zip");
8. string filename = Server.MapPath("DownLoad/aaa.zip");
9. Response.TransmitFile(filename);

}

//WriteFile实现下载
  protected void Button2_Click(object sender, EventArgs e)
  {

1. /*
2. using System.IO;
3. */
4. string fileName ="aaa.zip";//客户端保存的文件名
5. string filePath=Server.MapPath("DownLoad/aaa.zip");//路径
6. FileInfo fileInfo = new FileInfo(filePath);
7. Response.Clear();
8. Response.ClearContent();
9. Response.ClearHeaders();
10. Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
11. Response.AddHeader("Content-Length", fileInfo.Length.ToString());
12. Response.AddHeader("Content-Transfer-Encoding", "binary");
13. Response.ContentType = "application/octet-stream";
14. Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
15. Response.WriteFile(fileInfo.FullName);
16. Response.Flush();
17. Response.End();

}

//WriteFile分块下载
  protected void Button3_Click(object sender, EventArgs e)
  {

1. string fileName = "aaa.zip";//客户端保存的文件名
2. string filePath = Server.MapPath("DownLoad/aaa.zip");//路径
3. System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);
4. if (fileInfo.Exists == true)
5. {
6. 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
7. byte[] buffer = new byte[ChunkSize];
8. Response.Clear();
9. System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);
10. long dataLengthToRead = iStream.Length;//获取下载的文件总大小
11. Response.ContentType = "application/octet-stream";
12. Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));
13. while (dataLengthToRead > 0 && Response.IsClientConnected)
14. {
15. int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//读取的大小
16. Response.OutputStream.Write(buffer, 0, lengthRead);
17. Response.Flush();
18. dataLengthToRead = dataLengthToRead - lengthRead;
19. }
20. Response.Close();
21. }

}

//流方式下载
  protected void Button4_Click(object sender, EventArgs e)
  {

1. string fileName = "aaa.zip";//客户端保存的文件名
2. string filePath = Server.MapPath("DownLoad/aaa.zip");//路径
3. //以字符流的形式下载文件
4. FileStream fs = new FileStream(filePath, FileMode.Open);
5. byte[] bytes = new byte[(int)fs.Length];
6. fs.Read(bytes, 0, bytes.Length);
7. fs.Close();
8. Response.ContentType = "application/octet-stream";
9. //通知浏览器下载文件而不是打开
10. Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
11. Response.BinaryWrite(bytes);
12. Response.Flush();
13. Response.End();

}

转载原文：http://www.cnblogs.com/weixing/archive/2012/02/27/2369567.html