Handling the children of a parent-child relationship using Linq to XML

I am new trying to learn LINQ to XML and having trouble with "children". I have an XML file of info about documents; each document has some number of INDEX elements as in this snippet:

<DOCUMENTCOLLECTION>
<DOCUMENT>
<FILE filename="Z:\Consulting\ConverterRun4\B0000001\Submission\D003688171.0001.tif" outputpath="Z:\Consulting\ConverterRun4\B0000001\Submission"/>
<ANNOTATION filename=""/>
<INDEX name="CAN(idmDocCustom4)" value=""/>
<INDEX name="Comment(idmComment)" value="GENERAL CORRESPONDENCE 11-6-96 TO 10-29-"/>
<INDEX name="DiagnosticID(idmDocCustom5)" value="983958-0006.MDB-2155504"/>
<INDEX name="Document Class(idmDocType)" value="Submission"/>
<INDEX name="Original File Name(idmDocOriginalFile)" value="40410.TIF"/>
<INDEX name="Title(idmName)" value="1997-12"/>
<FOLDER name="/Accreditation/NCACIHE/1997-12"/>
</DOCUMENT>
<DOCUMENT>

I only need a few values from the INDEX elements - those with name attributes of:

Comment(idmComment)
Document Class(idmDocType)
Title(idmName)

This is what I have so far in my testing:

namespace ConsoleApplication1
{
class DocMetaData
{
    public string Comment { get; set; }
    public string DocClass { get; set; }
    public string Title { get; set; }
    public string Folder { get; set; }
    public string File { get; set; }
}
class Program
{
     static void Main(string[] args)
    {
        XDocument xmlDoc = XDocument.Load(@"convert.B0000001.Submission.xml");
        List<DocMetaData> docList = 
        (from d in xmlDoc.Descendants("DOCUMENT")
            select new DocMetaData
            {
                Folder = d.Element("FOLDER").Attribute("name").Value,
                File = d.Element("FILE").Attribute("filename").Value,
        // need Comment, DocClass, Title from d.Element("INDEX").Attribute("name")
            }
        ).ToList<DocMetaData>();

        foreach (var c in docList)
        {
            Console.WriteLine("File name = {0}", c.File);
            Console.WriteLine("\t" + "Folder = {0}", c.Folder);
        }
        Console.ReadLine();
    }
}

}

I don't think I want a List<Index> inside my DocMetaData class. I want to get rid of the one-to-many aspect of the INDEX elements within DOCUMENT and assign properties as shown in the DocMetaData class. I can't get my head around how to handle these children!

--------EDIT-UPDATE----27 May 2011 ----------------------

Made the following change whic开发者_如何学Pythonh caused compile error; have researched the error and tried some rearrangement of using directives but so far unable to get past this:

using System;
using System.Collections.Generic;
using System.Text;
using System.Xml.Linq;
using System.Xml.XPath;
using System.Linq;
namespace ConsoleApplication1
{
class DocMetaData
{
    public string Comment { get; set; }
    public string DocClass { get; set; }
    public string Title { get; set; }
    public string Folder { get; set; }
    public string File { get; set; }
}
class Program
{
static void Main(string[] args)
    {
        XDocument xmlDoc = XDocument.Load(@"convert.B0000001.Submission.xml");
        List<DocMetaData> docList = 
            (from d in xmlDoc.Descendants("DOCUMENT")
                select new DocMetaData
                {
                    Folder = d.Element("FOLDER").Attribute("name").Value,
                    File = d.Element("FILE").Attribute("filename").Value,
                    Comment = d.Element("INDEX")
                              .Where(i => i.Attribute("name") == "Comment(idmComment)")
                              .First()
                            .Attribute("value").Value
                }
            ).ToList<DocMetaData>();
        foreach (var c in docList)
        {
            Console.WriteLine("File name = {0}", c.File);
            Console.WriteLine("\t" + "Folder = {0}", c.Folder);
            Console.WriteLine("\t\t" + "Comment = {0}", c.Comment);
        }
        Console.ReadLine();
    }

Here is the error (NOTE: I have System.Xml.Linq as a Reference and a using directive for it also):

Error   1   'System.Xml.Linq.XElement' does not contain a definition for 'Where' and no   extension method 'Where' accepting a first argument of type 'System.Xml.Linq.XElement' could be found (are you missing a using directive or an assembly reference?)   C:\ProjectsVS2010\ConsoleApplication_LINQ\ConsoleApplication1\Program.cs    31  37  ConsoleApplication1

---

You probably want to get the INDEX elements and then use Where and First to get the one you want.

select new DocMetaData
{
    Folder = d.Element("FOLDER").Attribute("name").Value,
    File = d.Element("FILE").Attribute("filename").Value,
    Comment = d.Elements("INDEX")
               .Where(i => i.Attribute("name").Value == "Comment(idmComment)")
               .First()
               .Attribute("value").Value
    //similarly for other index elements
}

Note that this will throw an exception if there is not an INDEX element with the right attribute. If you want to ignore properties for which there is not a corresponding index, I would pull the select code into its own method, use FirstOrDefault, and do the appropriate null checks before assigning.

---

The secret lies in SelectMany. Here is a blog post that will help you wrap your head around the problem.

http://craigwatson1962.wordpress.com/2010/11/04/linq-to-xml-using-let-yield-return-and-selectmany/