Где хранить и как выводить данные

using System;
using System.Collections.Generic;
using System.Xml.Serialization;
 
public class Client
{
    public Client()
    {
    }
 
    public Client(int id, string phone)
    {
        this.Id = id;
        this.Phone = phone;
    }
 
    [XmlAttribute("id")]
    public int Id { get; set; }
 
    [XmlAttribute("name")]
    public string Phone { get; set; }
}
 
[XmlRoot("spam-base")]
public class SmsSpamBase
{
    public SmsSpamBase()
    {
        this.Clients = new List<Client>();
    }
 
    [XmlElement("client")]
    public List<Client> Clients { get; private set; }
}
 
class Program
{
    static void Main(string[] args)
    {
        SmsSpamBase spamBase = new SmsSpamBase();
        spamBase.Clients.AddRange(new [] {
            new Client(1, "+7 965 xx xx xxx"),
            new Client(2, "+7 987 xx xx xxx")
        });
        XmlSerializerNamespaces namespaces = new XmlSerializerNamespaces();
        namespaces.Add(string.Empty, string.Empty);
        XmlSerializer serializer = new XmlSerializer(typeof(SmsSpamBase));
        serializer.Serialize(Console.Out, spamBase, namespaces);
        Console.ReadLine();
    }
}