LazyPeople.cs

void Main()
{
	Person pete = new PersonFactory().GetPerson(1);
	
	Console.WriteLine(pete.Name);
}

public class Person
{
	public virtual int Id { get; protected set; }
	public virtual string Name { get; set; }
}

public class LazyPerson : Person
{
	private readonly PersonFactory loader;
	private bool loaded;
	private Person person;
	
	public LazyPerson(int id, PersonFactory loader)
	{
		Id = id;
		this.loader = loader;
	}
	
	public override string Name
	{
		get { EnsureLoaded(); return person.Name; }
		set { EnsureLoaded(); person.Name = value; }
	}
	
	private void EnsureLoaded()
	{
		if (loaded) return;
		
		person = loader.LoadPerson(Id);
		loaded = true;
	}
}

public class PersonFactory
{
	public Person GetPerson(int id)
	{
		return new LazyPerson(id, this);
	}
	
	public Person LoadPerson(int id)
	{
		return new Person { Name = "Pete Smith" };
	}
}