循环中AppendChild(1)的值添加不了，而AppendChild(0)和(2)却能添加。解决办法

<?xml version="1.0" encoding="utf-8"?>
<bookstore>
  <book genre="fantasy" ISBN="2-3631-4" old="29">
    <title>Oberon's Legacy</title>
    <author>Corets, Eva</author>
    <price>5.95</price>
  </book>
  <applenote genre="fantasy" ISBN="2-3631-4">
    <title>Oberon's Legacy</title>
    <author>Corets, Eva</author>
    <price>5.95</price>
  </applenote>
  <book genre="fantasy" ISBN="2-3631-6">
    <title>Oberon's Legacy</title>
    <author>Corets, Eva</author>
    <price>5.96</price>
  </book>
  <book genre="fantasy" ISBN="2-3631-6">
    <title>Oberon's Legacy</title>
    <author>Corets, Eva</author>
    <price>5.97</price>
  </book>
</bookstore>

            XmlElement xe1 = xmlDoc.CreateElement(childNodeName);//创建一个节点
            parentNode.AppendChild(xe1);//添加到父节点节点中 
            for (int i = 0; i < tmpXe.Count; i++)
            {
                xe1.AppendChild(tmpXe.Item(i));//将临时节点添加到新元素中
                xmlDoc.Save(xmlFile);
            }