使用C＃在XML文档中检索来自不同分支的父节点的叶子

Question

<Root>
  <P1 Text ="A" >
    <P2 Text = "AA">
      <P3 Text = "AAA">
        <L Text = "l_A"/>
        <L Text = "l_B"/>
        <L Text = "l_C"/>
      </P3>
      <P3 Text = "BBB">
        <L Text = "l_D"/>
        <L Text = "l_E"/>
        <L Text = "l_F"/>
      </P3>
    </P2>
    <P2 Text = "BB">
       <L Text = "l_G"/>
       <L Text = "l_H"/>
       <L Text = "l_I"/>
    </P2>
  </P1>
</Root>  

From an XML document containing thousands of variably nested nodes up to 10 levels deep, I would like to retrieve programmatically only the leaves belonging to any of the "P" parents as follows: for instance, in the example above, selecting P2 "AA" would yield l_A to l_F and P3 "BBB" would give l_D to l_F.

Answer 1

Something like this (returns a list of strings):

    XDocument doc = XDocument.Load(@"test.xml");

    string level = "P3";
    string levelAttr = "AAA";

    var list = (from d in doc.Descendants(level)
                let xAttribute = d.Attribute("Text")
                where xAttribute != null && xAttribute.Value == levelAttr
                from l in d.Descendants("L")
                let lAttribute = l.Attribute("Text")
                where lAttribute != null
                select lAttribute.Value);

You may remove the attribute null checks if the Text attribute is always there...

Answer 2

one way is using XPath by XmlDocument (if you not using LINQ )

your XPath may be like this:

//P2[@Text='AA']//L/@Text

and your code like this:

XmlDocument document; //init and load it

static List<String> GetLeavesText(int pLevel /* 2 */, string pText /* AA */)
{
    var result = new List<String>();

    //loaded document

    var nodeList = document.SelectNodes(String.Format(@"//P{0}[@Text='{1}']//L/@Text", pLevel, pText));
    if (nodeList != null)
        foreach (XmlNode xmlNode in nodeList)
        {
            result.Add(xmlNode.InnerText);
        }

    return result;
}