asp.net 下载文件（图片、word、excel等）

    string filePath = Server.MapPath("~/excel.xlsx");
        if (File.Exists(filePath))
        {
            FileStream fs = new FileStream(filePath, FileMode.Open);
            byte[] bytes = new byte[(int)fs.Length];
            fs.Read(bytes, , 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(Path.GetFileName(filePath), System.Text.Encoding.UTF8));
            Response.BinaryWrite(bytes);
            Response.Flush();
            Response.End();
        }