Adding an instance to reference that is field in another instance

问题

Excuse me, this question maybe exist in a different form but I really searched everywhere and don't see it.

I have worked in C++ and am used to pointers. I am having problem with substituting my logic with C# analogue code.

Here is my C# code:

class Parent
    {
        public Parent A { get; set; }
        public Parent B { get; set; }

    }

    static void Main(string[] args)
    {

        Parent P1 = new Parent();
        Parent X = new Parent();
        Parent[] array = new Parent[10];
        array[0] = P1;
        array[1] = P1.A;
        array[2] = P1.B;   

        array[1]= X;

        //I expect P1.A to be X but it is null
    }

I have seen that there are pointers in C# but is there a better way to do this? Thanks

Edit:

My question wasn't complete. I am sorry. This is the code:

abstract class Parent
    {

        protected virtual int foo();
    }

    public class Son : Parent
    {
        public Parent A { get; set; }
        public Parent B { get; set; }

        protected override int foo()
        {
             return base.foo();
        }

    }

    public class Daughter : Parent
    {
        public Parent A { get; set; }
        public Parent B { get; set; }
    }

    static void Main(string[] args)
    {

        Son P1 = new Son();
        Parent X = new Daughter();
        Parent[] array = new Parent[10];
        array[0] = P1;
        array[1] = P1.A;
        array[2] = P1.B;   

        array[1]= X;

        //I expect P1.A to be X but it is null
    }

回答1:

What you wan t to do is:

      array[1].A = X;

回答2:

It is null because it isn't initialized.

You must initialize properties.

class Parent
{
    public Parent A { get; set; }
    public Parent B { get; set; }

    Parent(Parent a, Parent b)
    {
        A = a;
        B = b;
    }
}

and

Parent X = new Parent();
Parent P1 = new Parent(X, new Parent());

来源：https://stackoverflow.com/questions/33566922/adding-an-instance-to-reference-that-is-field-in-another-instance

标签

arrays

pointers

reference