gistfile1.cs

public class Person
{
   public string Name{get;set;}
   public Automobile Car {get;set;}
}

public class Automobile
{
  public string Name {get;set;}
  public string Colour {get;set;}
}

Person myPerson = db.Load<Person>("2");
myPerson.Name = "Its Fred";

db.Save<Person>(myPerson);