C# 流方式下载文件

 //客户端保存的文件名
 string fileName = "222.xls";
 //被下载文件的服务器绝对路径
 string filePath = Server.MapPath("file/" + doc.FileName);

 Response.Clear(); //清空缓存

 //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]; //获取文件字节长度
 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();
 //下载完成后删除文件
 File.Delete(Server.MapPath("file/" + doc.FileName)); 
 Response.End();