Create a deep object graph with Linq to XML, refactoring?

Question

I am writing a simple XML file parser using LINQ to XML.

I want to have a TreeNode object (i.e a simple Tree structure) for each element in the XML. I want each element to be strongly typed.

It looks ugly and redundant compared to the simple looping approach I was using before (using System.XML). Is there a way to strip out the redundancies here?

        XElement ops = XElement.Load(@"c:\temp\exp.xml");
        Tree<Element> domain = new Tree<Element>();
        domain.Root = new TreeNode<Element>();
        var cells =
                    from cell in ops.Elements("cell")
                    select new
                    {
                        TreeNodeObj = new TreeNode<Element>
                            (new Cell((string)cell.Attribute("name"), (string)cell.Attribute("name"), null)),
                        XElem = cell
                    };
        foreach (var cell in cells)
        {
            domain.Root.AddChild(cell.TreeNodeObj);
            var agents =
                    from agent in cell.XElem.Elements("agent")
                    select new
                    {
                        TreeNodeObj = new TreeNode<Element>
                            (new Agent((string)agent.Attribute("name"), (string)agent.Attribute("name"), null)),
                        XElem = agent
                    };
            foreach (var agent in agents)
            {
                cell.TreeNodeObj.AddChild(agent.TreeNodeObj);
                var nas =
                    from na in agent.XElem.Elements("node-agent")
                    select new
                    {
                        TreeNodeObj = new TreeNode<Element>
                            (new NodeAgent((string)na.Attribute("name"), (string)na.Attribute("name"), null)),
                        XElem = agent
                    };
                foreach (var na in nas)
                {
                    agent.TreeNodeObj.AddChild(na.TreeNodeObj);
                }
            }
        }

Answer 1

Without your classes and source xml, it's quite hard to provide you with the exact code you're after, but here's how I like to structure my XML parsing:

XDocument d = XDocument.Parse(@"<a id=""7""><b><c name=""foo""/><c name=""bar""/></b><b/><b2/></a>");
var ae = d.Root;

var a = new A
    {
        Id = (int)ae.Attribute("id"),
        Children = new List<B>(ae.Elements("b").Select(be => new B
        {
            Children = new List<C>(be.Elements("c").Select(ce => new C
            {
                Name = (string)ce.Attribute("name")
            }))
        }))
    };

Given the xml:

<a>
  <b>
    <c name="foo"/>
    <c name="bar"/>
  </b>
  <b/>
  <b2/>
</a>

and the classes:

class A
{
    public int Id { get; set; }
    public List<B> Children { get; set; }
}
class B
{
    public List<C> Children { get; set; }
}
class C
{
    public string Name { get; set; }
}

Answer 2

It is hard to answer this fully without sample data and actual types, but I would refactor it like below.

From the original example, I'm assuming we don't want to mess with the constructors of the entities (Agent etc), and that we want to retain the separate "TreeNode<T>" model, putting our entities inside the tree (rather than changing the entities to model things as associated collections). I've also assumed that we can take more liberties with TreeNode<T> than we can with the entities, so I've introduced a constructor that accepts IEnumerable<...>, since this allows use with LINQ sub-queries:

XElement ops = XElement.Load(@"c:\temp\exp.xml");
Tree<Element> domain = new Tree<Element>(
    from cell in ops.Elements("cell")
    select new TreeNode<Element>(
        new Cell(
            (string)cell.Attribute("name"),
            (string)cell.Attribute("name"), null
        ),
        from agent in cell.Elements("agent")
        select new TreeNode<Element>(
            new Agent(
                (string)agent.Attribute("name"),
                (string)agent.Attribute("name"), null
            ),
            from na in agent.Elements("node-agent")
            select new TreeNode<Element>(
                new NodeAgent(
                    (string)na.Attribute("name"),
                    (string)na.Attribute("name"), null
                )
            )
        )
    )
);

With framework code below:

using System.Collections.Generic;
using System.Linq;
using System.Xml.Linq;
class Tree<T>
{
    public TreeNode<T> Root { get; set; }
    public Tree() { }
    public Tree(IEnumerable<TreeNode<T>> children)
    {
        Root = new TreeNode<T>(children);
    }
}
class TreeNode<T>
{
    private List<TreeNode<T>> children;
    public IList<TreeNode<T>> Children
    {
        get
        {
            if (children == null) children = new List<TreeNode<T>>();
            return children;
        }
    }
    private readonly T value;
    public TreeNode() { }
    public TreeNode(T value) { this.value = value; }
    public TreeNode(T value, IEnumerable<TreeNode<T>> children)
            : this(children)
    {
        this.value = value;
    }
    public TreeNode(IEnumerable<TreeNode<T>> children)
    {
        children = new List<TreeNode<T>>(children);
    }
}
class Element { }
class Cell : Element {
    public Cell(string x, string y, string z) { }
}
class Agent : Element {
    public Agent(string x, string y, string z) { }
}
class NodeAgent : Element {
    public NodeAgent(string x, string y, string z) { }
}
static class Program
{
    static void Main()
    {
        XElement ops = XElement.Load(@"c:\temp\exp.xml");
        Tree<Element> domain = new Tree<Element>(
            from cell in ops.Elements("cell")
            select new TreeNode<Element>(
                new Cell(
                    (string)cell.Attribute("name"),
                    (string)cell.Attribute("name"), null
                ),
                from agent in cell.Elements("agent")
                select new TreeNode<Element>(
                    new Agent(
                        (string)agent.Attribute("name"),
                        (string)agent.Attribute("name"), null
                    ),
                    from na in agent.Elements("node-agent")
                    select new TreeNode<Element>(
                        new NodeAgent(
                            (string)na.Attribute("name"),
                            (string)na.Attribute("name"), null
                        )
                    )
                )
            )
        );
    }
}