Question

I am really confused about object relationships!
I have two classes Person and Address. Here are the details:

 public class Person
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }

        private List<Address> _addresses = new List<Address>(); 

        public void AddAddress(Address address)
        {
            _addresses.Add(address);
            address.Person = this; 
        }

        public List<Address> Addresses  
        {
            get { return _addresses; }
            set { _addresses = value; }
        }
    }

  public class Address
    {
        public string Street { get; set; }


        public Person Person
        {
            get; set;
        }
    }

The AddAddress method in the Person class adds the address to the Addresses collection and also sets the Person for the Address object. Now, in the code I do the following:

var person = new Person() { FirstName = "John", LastName = "Doe" };
            person.AddAddress(new Address() { Street = "Blah Blah" });

            person.Addresses[0].Person = null; 

I am thinking that it should set the person object to null since Addresses[0].Person is pointing to the original person object. But it is not setting it to null. What is going on here?

Answer 1

What is going on here?

Simple Explanation:

A variable, in this case ‘Person’, holds a reference to the object. Under the hood, this is just a number. When you assign it to null, what you are doing is just stopping that variable pointing at the object. The object itself still exists.

— Edit

A way to understand how this works, is to literally stand near your computer, and point at it. You are now a variable, and your computer is an object. Now stop pointing at the computer (put your arm down). Now you are a variable that has been assigned null. The computer still exists, nothing has changed about it, the only difference is that you now no-longer point at it.