使用C#和Lambda，如何从嵌套List<>的属性中获取不同的列表？

class Person
{
    public string Name { get; set; }
    public List<Address> Addresses { get; set; }
}

class Address
{
    public string City { get; set; }
    public List<string> PhoneNumbers { get; set; }
}

List<Person> persons = new List<Person>
{
    new Person
    {
        Name = "John",
        Addresses = new List<Address>
        {
            new Address { City = "New York", PhoneNumbers = new List<string> { "123", "456" } },
            new Address { City = "London", PhoneNumbers = new List<string> { "789" } }
        }
    },
    new Person
    {
        Name = "Alice",
        Addresses = new List<Address>
        {
            new Address { City = "Paris", PhoneNumbers = new List<string> { "321" } }
        }
    }
};

List<string> phoneNumbers = persons
    .SelectMany(p => p.Addresses) // 展开嵌套的Addresses列表
    .SelectMany(a => a.PhoneNumbers) // 展开嵌套的PhoneNumbers列表
    .ToList();

foreach (string phoneNumber in phoneNumbers)
{
    Console.WriteLine(phoneNumber);
}