Зациклить файл XML и добавить в список С#

Пожалуйста, попробуйте этот пример:
XML:

 <?xml version = "1.0" encoding = "utf-8" standalone = "yes"?>
<root>
    <Brand name = "Brand1">
        <product name = "Product1" />
        <product name = "Product2" />
    </Brand>
    <Brand name = "Brand2">
        <product name = "Product3" />
        <product name = "Product4" />
    </Brand>
</root>

С#:

                StringBuilder result = new StringBuilder();
                foreach (XElement level1Element in XElement.Load(@"D:\product.xml").Elements("Brand"))
                {
                    result.AppendLine(level1Element.Attribute("name").Value);
                    foreach (XElement level2Element in level1Element.Elements("product"))
                    {
                        result.AppendLine("  " + level2Element.Attribute("name").Value);
                    }
                }

Попробуйте xml linq:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
using System.Xml.Linq;


namespace ConsoleApplication108
{
    class Program
    {
        const string FILENAME = @"c:\temp\test.xml";
        static void Main(string[] args)
        {
            XDocument doc = XDocument.Load(FILENAME);

            var results = doc.Descendants("PasswordSettings").Select(x => new
            {
                c = (string)x.Element("CustomerRef"),
                node = (string)x.Element("Node"),
                name = (string)x.Element("Name"),
                login = (string)x.Element("Login"),
                password = (string)x.Element("Password"),
                fileType = (string)x.Element("FileType")
            }).ToList();

        }
    }
}