C#根据流下载文件

c#从服务器下载文件可以使用下面4个方法：transmitfile、writefile、writefile和流方式下载文件，并保存为相应类型，方法如下：

1、transmitfile实现下载
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/z.zip");
        response.transmitfile(filename);
    }
2、writefile实现下载
protected void button2_click(object sender, eventargs e)
    {
        /* 
        using system.io;
 
        */
        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();
    }
3、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();
        }
    }
4、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();
    }