Export功能 导致 页面显示很多非法字符，还可能页面显示两次

        private void exportBinaryToExcel(byte[] bytes, string filename)
        {
            Response.AddHeader("Content-Disposition", "attachment; filename=" + filename);
            Response.AddHeader("Content-Length", bytes.Length.ToString());
            Response.ContentType = "application/octet-stream";
            Response.BinaryWrite(bytes);
            Response.Flush();
            Response.End(); //这里的问题
        }