gistfile1.cs

namespace PropertyDefaultAttributeTestConsole
{
    class Program
    {
        static void Main(string[] args)
        {
            Person pat = new Person();
            Console.WriteLine(pat); // "Caldwell, Pat"
            Console.WriteLine(pat.Fiance); // "Woody, Lauren"

            Console.WriteLine(pat.Friends.Count); // 0
            pat.Friends.Add(new Person("James", "Brechtel"));
            Console.WriteLine(pat.Friends.Count); // 1

            pat.FirstName = "Patrick";

            Console.WriteLine(pat); // "Caldwell, Patrick"
            Console.ReadLine();
        }
    }

    class Person
    {
        public Person(string first, string last)
        {
            FirstName = first;
            LastName = last;
        }

        public Person()
        { }

        [PropertyDefault(DefaultValue = "Pat")]
        public string FirstName { get; set; }

        [PropertyDefault(DefaultValue = "Caldwell")]
        public string LastName { get; set; }

        [PropertyDefault("Please enter a profile!")]
        public StringBuilder Profile { get; set; }

        [PropertyDefault]
        public List<Person> Friends { get; set; }

        [PropertyDefault("Lauren", "Woody")]
        public Person Fiance { get; set; }

        public override string ToString()
        {
            return string.Format("{0}, {1}", LastName, FirstName);
        }
    }
}