asp.net下载文件几种方式

protected void Button1_Click(object sender, EventArgs e)   {
  /*   微软为Response对象提供了一个新的方法TransmitFile来解决使用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);   
  }

  //WriteFile实现下载  
protected void Button2_Click(object sender, EventArgs e)   {   
/*   using System.IO;       */
  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   
protected void Button3_Click(object sender, EventArgs e)   {
    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  
protected void Button4_Click(object sender, EventArgs e)   
{   
       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();
  }