C#，asp，指定位置插入XML数据

xml文件：
<?xml version="1.0" encoding="utf-8"?>
<playlist>
<trackList>
<track>
<location>Silence.mp3</location>
<title>Silence</title>
</track>
<track>
<location>Highhopes.mp3</location>
<title>Highhopes</title>
</track>
</trackList>
</playlist>
然后修改 xmlDoc.DocumentElement.AppendChild(xM); 这句，修改为：xmldocSelect.AppendChild(xM);