using System;

using System.Xml;

using System.Xml.Linq;

using System.Linq;

using System.Xml.XPath;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var raw = @"<?xml version='1.0' encoding='utf-8'?>

<database>

    <user list='default'>

        <list nom='Nom' description='Description' image='no_image.png'/>

    </user>

    <user list='otherListName'>

        <list nom='' description='' image=''/>

        <list nom='' description='' image=''/>

    </user>

</database>";

        var doc = XDocument.Parse(raw);

        var listName = "default";

        var result = doc.Root.Elements("user").Where(o => (string)o.Attribute("list") == listName).Elements("list");

        foreach(var r in result)

        {

            Console.WriteLine(r.ToString());

        }

    }

}