asp.net实现下载

1.TransmitFile下载

    protected void Button1_Click(object sender, EventArgs e)
    {
        Response.ContentType = "application/x-rar-compressed"; //设置输出流的Http MIME的类型
        Response.AddHeader("Content-Disposition", "attachment;filename=test.rar"); //讲一个http标头添加到输出流
        string filename = Server.MapPath("test.rar"); //获取物理路径
        Response.TransmitFile(filename);
    }

2.WriteFile下载

    protected void Button2_Click(object sender, EventArgs e)
    {
        string fileName = "test.rar"; //客户端保存的文件名
        string filePath = Server.MapPath("test.rar"); //服务器物理路径

        FileInfo fileInfo = new FileInfo(filePath);
        Response.Clear();//清除缓冲流中所有内容
        Response.ClearContent();//清除缓冲区中的所有内容输出
        Response.ClearHeaders();//清除缓冲区流中的所有头
        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();//向客户端发送当前缓冲流的输出
        Response.End();
    }

3.WriteFile分块下载

    protected void Button3_Click(object sender, EventArgs e)
    {
        string fileName = "test.rar";//客户端保存的文件名
        string filePath = Server.MapPath("test.rar");//下载文件的服务器物理路径

        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100K，这样可以缓解服务器的压力
            byte[] buffer = new byte[ChunkSize]; //字节数组,大小：102400字节

            Response.Clear();//清除缓冲区中所有内容
            System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);
            long dataLengthToRead = iStream.Length;//获取下载的文件的总大小
            Response.ContentType = "application/octet-stream"; //MIME 类型
            Response.AddHeader("Content-Disposition","attachment;filename=" + HttpUtility.UrlEncode(fileName));
            while (dataLengthToRead > 0 && Response.IsClientConnected)
            {
                int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//从中读取字节块并将该内容写入缓冲区
                Response.OutputStream.Write(buffer, 0, lengthRead) ;
                Response.Flush();//向客户端发送当前所有缓冲区的输出
                dataLengthToRead = dataLengthToRead - lengthRead;
            }
            Response.Close();
        }
    }

4.流方式下载

    protected void Button4_Click(object sender, EventArgs e)
    {
        string fileName = "test.rar";//客户端保存的文件名
        string filePath = Server.MapPath("test.rar");//下载文件在服务器的物理路径

        //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();
    }