Asp.Net 之 下载文件的常用方式

1、直接使用Response.TransmitFile(filename)方法

    protected void Button_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");
　　　　 //将指定的文件直接写入 HTTP 响应输出流，而不在内存中缓冲该文件。
        Response.TransmitFile(filename);
    }

2、WriteFile实现下载

    protected void Button_Click(object sender, EventArgs e)
    {
        /* using System.IO; */

        string fileName = "aaa.zip";//服务端保存的文件名
        string filePath = Server.MapPath("DownLoad/aaa.zip");//路径

        System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);
        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");
        //将指定文件的内容作为文件块直接写入 HTTP 响应输出流。
        Response.WriteFile(fileInfo.FullName);
        Response.Flush();
        Response.End();
    }

3、WriteFile分块下载

    protected void Button_Click(object sender, EventArgs e)
    {
        string fileName = "aaa.zip";//服务端保存的文件名
        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)
            {
                //从流中读取字节块并将该数据写入给定缓冲区中
                //返回结果:读入缓冲区中的总字节数。
                //如果当前的字节数没有所请求那么多，则总字节数可能小于所请求的字节数；如果已到达流的末尾，则为零。
                int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//读取的大小
                //当在派生类中重写时，向当前流中写入字节序列，并将此流中的当前位置提升写入的字节数。
                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.zip";//服务端保存的文件名
        string filePath = Server.MapPath("DownLoad/aaa.zip");//路径

        //以字符流的形式下载文件
        System.IO.FileStream fs = new System.IO.FileStream(filePath, System.IO.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));
        //将一个二进制字符串写入 HTTP 输出流
        Response.BinaryWrite(bytes);
        Response.Flush();
        Response.End();
    }