formatting_xml_6.cs

public class Person
{
    [XmlElement(ElementName = "First")]
    public string FirstName { get; set; }

    [XmlElement(ElementName = "Last")]
    public string LastName { get; set; }

    public int Age { get; set; }

    [XmlElement(IsNullable = true)]
    public string Email { get; set; }

    public PhoneNumber[] PhoneNumbers { get; set; }

    public bool ShouldSerializeAge()
    {
        // Only serialize Age if 18 or older
        return Age >= 18;
    }
}

public class PhoneNumber
{
    [XmlIgnore]
    public string AreaCode { get; set; }

    [XmlIgnore]
    public string Number { get; set; }

    [XmlText]
    public string FormattedNumber
    {
        get { return $"{AreaCode}-{Number}"; }
        set {}
    }
}