Convert flat XML to hierarchical structure using LINQ

Question

I have an XML document in a flat format:

<root>
   <node-one>
      <parent-id />
      <node-id>1</node-id>
      <value>foo</value>
   </node-one>
   <node-two>
      <parent-id>1</parent-id>
      <node-id>2</node-id>
      <value>bar</value>
   </node-two>
   <node-three>
      <parent-id>1</parent-id>
      <node-id>3</node-id>
      <value>baz</value>
   </node-three>
   <node-four>
      <parent-id>3</parent-id>
      <node-id>4</node-id>
      <value>qux</value>
   </node-four>
</root>

I want to convert it to hierarchical tree-like structure like this:

<root>
   <node-one>
      <parent-id />
      <node-id>1</node-id>
      <value>foo</value>
      <node-two>
         <parent-id>1</parent-id>
         <node-id>2</node-id>
         <value>bar</value>
      </node-two>
      <node-three>
         <parent-id>1</parent-id>
         <node-id>3</node-id>
         <value>baz</value>
         <node-four>
            <parent-id>3</parent-id>
            <node-id>4</node-id>
            <value>qux</value>
         </node-four>
      </node-three>
   </node-one>
</root>

Is there an elegant way to achieve it using XmlDocument/XDocument ? Any help would greatly appreciated.

Answer 1

Try a recursive algorithm

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Linq;


namespace ConsoleApplication4
{
    class Program
    {
        const string FILENAME = @"c:\temp\test.xml";
        static List<XElement> nodes;
        static void Main(string[] args)
        {
            XDocument doc = XDocument.Load(FILENAME);

            nodes = doc.Root.Elements().ToList();

            XElement parent = new XElement("root");
            RecursvieAdd(parent, "");
            XDocument doc2 = new XDocument(parent);
        }
        static void RecursvieAdd(XElement parent, string parentId)
        {
            foreach(XElement child in nodes.Where(x => (string)x.Element("parent-id") == parentId))
            {
               XElement newChild = new XElement(child);
               parent.Add(newChild);
               string id = (string)child.Element("node-id");
               RecursvieAdd(newChild, id);
            }

        }
    }

}