.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=CodeShark.zip");
         string filename = Server.MapPath("DownLoad/CodeShark.zip");
         Response.TransmitFile(filename);
     }

protected void Button2_Click(object sender, EventArgs e)
    ...{
        string fileName = "CodeShark.zip";//客户端保存的文件名
    string filePath = Server.MapPath("DownLoad/CodeShark.doc");//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();
    }

 protected void Button3_Click(object sender, EventArgs e)
    ...{
        string fileName = "CodeShark.zip";//客户端保存的文件名
    string filePath = Server.MapPath("DownLoad/CodeShark.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();
        }
    }

 protected void Button4_Click(object sender, EventArgs e)
    ...{
        string fileName = "CodeShark.zip";//客户端保存的文件名
    string filePath = Server.MapPath("DownLoad/CodeShark.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();
    }