学步园

FileStream r = null;
        try
        {
            r = new FileStream(filepath, FileMode.OpenOrCreate);
            //设置基本信息
            Response.Buffer = false;
            Response.AddHeader("Connection", "Keep-Alive");
            Response.ContentType = "application/octet-stream";
            Response.AddHeader("Content-Disposition", "attachment;filename=" + Path.GetFileName(HttpUtility.UrlEncode(filepath)));
            Response.AddHeader("Content-Length", r.Length.ToString());

            while (true)
            {
                //开辟缓冲区空间
                byte[] buffer = new byte[1024];
                //读取文件的数据
                int leng = r.Read(buffer, 0, 1024);
                if (leng == 0)//到文件尾，结束
                    break;
                if (leng == 1024)//读出的文件数据长度等于缓冲区长度，直接将缓冲区数据写入
                {
                    Response.BinaryWrite(buffer);
                }

                else
                {
                    //读出文件数据比缓冲区小，重新定义缓冲区大小，只用于读取文件的最后一个数据块
                    byte[] b = new byte[leng];
                    for (int i = 0; i < leng; i++)
                        b[i] = buffer[i];

                    Response.BinaryWrite(b);
                }
            }

            r.Close();//关闭下载文件
            Response.End();//结束文件下载
        }
        catch (Exception e)
        {
            r.Close();//关闭下载文件
            Response.End();//结束文件下载
            string str = e.Message;
        }