使用Linq到XML处理父子关系的子代

<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>

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

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();
    }
}

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();
    }

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