c# 下载文件

private void DownLoadFile(string fileName, string downName)
    {
        System.IO.FileStream r = new System.IO.FileStream(fileName, System.IO.FileMode.Open);    //文件下载实例化
        //设置基本信息  
        Response.Buffer = false;
        Response.AddHeader("Connection", "Keep-Alive");
        Response.ContentType = "application/octet-stream";
        downName = System.Web.HttpUtility.UrlEncode(downName, System.Text.Encoding.UTF8);
        //Response.AddHeader("Content-Disposition", "attachment;filename=" + ToHexString(downName));
        Response.AddHeader("Content-Disposition", "attachment;filename=" + downName);
        Response.AddHeader("Content-Length", r.Length.ToString());

        while (true)    //如果文件大于缓冲区，通过while循环多次加载文件
        {
            //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);           //向客户端发送数据流
            }
            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
    }