先列出代码，过段时间再写说明

protected void Page_Load(object sender, EventArgs e) { string file = Request["file"]; if (string.IsNullOrEmpty(file)) return; string filepath = Server.MapPath("~/Download/" + file); if (File.Exists(filepath)) //DownLoadStreamFile(filepath); ToOpen(filepath, ""); Response.End(); } /// <summary> /// 下载文件 /// </summary> /// <param name="serverfilpath"></param> /// <param name="filename"></param> public static void ToDownload(string serverfilpath, string filename) { FileStream fileStream = new FileStream(serverfilpath, FileMode.Open); long fileSize = fileStream.Length; HttpContext.Current.Response.ContentType = "application/octet-stream"; HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=\"" + UTF_FileName(filename) + "\";"); attachment --- 作为附件下载 inline --- 在线打开 HttpContext.Current.Response.AddHeader("Content-Length", fileSize.ToString()); byte[] fileBuffer = new byte[fileSize]; fileStream.Read(fileBuffer, 0, (int)fileSize); HttpContext.Current.Response.BinaryWrite(fileBuffer); fileStream.Close(); HttpContext.Current.Response.End(); } /// <summary> /// 打开文件 /// </summary> /// <param name="serverfilpath"></param> /// <param name="filename"></param> public static void ToOpen(string serverfilpath, string filename) { FileStream fileStream = new FileStream(serverfilpath, FileMode.Open); long fileSize = fileStream.Length; HttpContext.Current.Response.ContentType = "application/octet-stream"; HttpContext.Current.Response.AddHeader("Content-Disposition", "inline; filename=\"" + UTF_FileName(filename) + "\";"); HttpContext.Current.Response.AddHeader("Content-Length", fileSize.ToString()); byte[] fileBuffer = new byte[fileSize]; fileStream.Read(fileBuffer, 0, (int)fileSize); HttpContext.Current.Response.BinaryWrite(fileBuffer); fileStream.Close(); HttpContext.Current.Response.End(); } private static string UTF_FileName(string filename) { return HttpUtility.UrlEncode(filename, System.Text.Encoding.UTF8); } /// <summary> /// 下载文件数据流 /// </summary> /// <param name="serverfilpath"></param> public static void DownLoadStreamFile(string serverfilpath) { int blocksize = 1024 * 100; byte[] buffer = new byte[blocksize]; byte[] fileHeader = new byte[101]; int startindex = 0; int bytesread = 0; int bytesfinish = 0; int filesize = 0; string headerText = string.Empty; BinaryReader bReader = null; bReader = new BinaryReader(File.OpenRead(serverfilpath)); filesize = Convert.ToInt32(bReader.BaseStream.Length); while (bytesfinish < filesize) { if (bytesfinish + blocksize < filesize) bytesread = bReader.Read(buffer, startindex, blocksize); else bytesread = bReader.Read(buffer, startindex, filesize - bytesfinish); bytesfinish += bytesread; HttpContext.Current.Response.OutputStream.Write(buffer, 0, bytesread); } bReader.Close(); HttpContext.Current.Response.End(); }