My name
is
Jon Skeet

Create a list of attribute of nested nodes from XML file

I have an XML file as following:

<?xml version="1.0" encoding="utf-8"?>
<files>
    <file name="1">
        <file name="4">     
        </file> 
    </file>
    <file name="2">
    </file>
    <file name="3">
        <file name="5">
            <file name="7">
            </file>
        </file>
    </file>
</files>

Now I want to create a list of strings/numbers which save all the attribute name in a list/array which has the nested nodes hierarchy in it. For example for the above XML file the expected list would be,

(1,4
2
3,5,7)

Because I could could know the desired node in which level is.

Would you please let me know what is your idea about having such a list?

Update: After Jon's answer, If the children nodes are in the same hierarchy, then would in the following way.

The XML file:

<files>
<file name="1">
    <file name="4"/>     
    <file name="2">
      <file name="3"/>
    </file> 
</file>
<file name="5"/>

and the desired output:

1,4
1,2
1,2,3
5

PS. After testing for some examples I noticed that I have to have first parent and then children in case when there are two or more children from the same level.

It seems that you possibly want:

For all file elements which don't have a child file element
Work out the file element ancestry
Take the name attribute for each ancestor, and join it together

So I think this should work, creating an IEnumerable<List<int>>:

var hierarchy = doc.Descendants("file")
                   .Where(x => x.Element("file") == null)
                   .Select(x => x.AncestorsAndSelf("file")
                                 .Reverse()
                                 .Select(f => (int) f.Attribute("name"))
                                 .ToList());

Complete example:

using System;
using System.Linq;
using System.Xml.Linq;

class Test
{
    static void Main()
    {
        var doc = XDocument.Load("test.xml");
        var hierarchy = doc.Descendants("file")
                   .Where(x => x.Element("file") == null)
                   .Select(x => x.AncestorsAndSelf("file")
                                 .Reverse()
                                 .Select(f => (int) f.Attribute("name"))
                                 .ToList());

        foreach (var item in hierarchy)
        {
            Console.WriteLine(string.Join(", ", item));
        }
    }
}

Output:

1, 4
2
3, 5, 7

An alternative approach is to take all top-level file elements, and for each one, find all the descendants:

using System;
using System.Linq;
using System.Xml.Linq;

class Test
{
    static void Main()
    {
        var doc = XDocument.Load("test.xml");
        var hierarchy = doc.Root.Elements("file")
                   .Select(x => x.DescendantsAndSelf("file")
                                 .Select(f => (int) f.Attribute("name"))
                                 .ToList());

        foreach (var item in hierarchy)
        {
            Console.WriteLine(string.Join(", ", item));
        }
    }
}

Now both of those give the same result at the moment, because you've basically got a "line" from each top-level file element. However, you should consider what you want the result to be if you had XML like this:

<files>
    <file name="1">
        <file name="4"/>     
        <file name="2">
          <file name="3"/>
        </file> 
    </file>
    <file name="5"/>
</files>

Here the top-level element with name 1 has two children - what would you want the result to be?

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