如何将节点放入父节点？

Question

我想添加一个具有属性的父节点，并将节点置于该父节点内。我有以下xml：

<?xml version="1.0" encoding="UTF-8"?>
<foo>
   <row>
      <PHONE_NUM>124</PHONE_NUM>
      <PHONE_ORDER>1</PHONE_ORDER>      
   </row>
   <row>
      <PHONE_NUM>123</PHONE_NUM>
      <PHONE_ORDER>2</PHONE_ORDER>      
   </row>
   <row>
      <PHONE_NUM>181</PHONE_NUM>
      <PHONE_ORDER>3</PHONE_ORDER>      
   </row>   
</foo>

我已经尝试过这种方法：

var xmlString = @"<?xml version=""1.0"" encoding=""UTF-8""?>
    <foo>
       <row>
          <PHONE_NUM>124</PHONE_NUM>
          <PHONE_ORDER>1</PHONE_ORDER>      
       </row>
       <row>
          <PHONE_NUM>123</PHONE_NUM>
          <PHONE_ORDER>2</PHONE_ORDER>      
       </row>
       <row>
          <PHONE_NUM>181</PHONE_NUM>
          <PHONE_ORDER>3</PHONE_ORDER>      
       </row>   
    </foo>";

var report = XDocument.Parse(xmlString);
var newdoc = new XDocument();
newdoc.Add(new XElement("testsuites")); 
newdoc.Root.Add(report.Root);

但是上面的代码生成的是id，而命令books已成为根：

<books>
  <foo>
      <row>
          <PHONE_NUM>124</PHONE_NUM> 
          <PHONE_ORDER>1</PHONE_ORDER> 
      </row>
      <row>
          <PHONE_NUM>123</PHONE_NUM> 
          <PHONE_ORDER>2</PHONE_ORDER> 
      </row>
      <row>
          <PHONE_NUM>181</PHONE_NUM> 
          <PHONE_ORDER>3</PHONE_ORDER> 
      </row>
      </foo>
  </books>

我想要实现的是：

<?xml version=""1.0"" encoding=""UTF-8""?>
<foo>
    <books id=""1"">
       <row>
          <PHONE_NUM>124</PHONE_NUM>
          <PHONE_ORDER>1</PHONE_ORDER>      
       </row>
       <row>
          <PHONE_NUM>123</PHONE_NUM>
          <PHONE_ORDER>2</PHONE_ORDER>      
       </row>
       <row>
          <PHONE_NUM>181</PHONE_NUM>
          <PHONE_ORDER>3</PHONE_ORDER>      
       </row>  
    </books>
</foo>

[如果可能，如果使用XmlDocument类，那就太好了。任何帮助将不胜感激。