How to Pass objects between classes

Question

So what I'm trying to do here is pass the same copy of a class (class A) to another class (class B), but class B is instanced in class A.

Using a new statement in class B won't work because it would cause an infinite loop, as well as creating a new instance of it, when I want to be able to use variables from the 1st instance of class A.

I know about object.equals() but I can't use it until I define the class A's object in class B. Just using object.equals results in a null reference.

public partial class class_A : Form
{
    public class_B _class_B = new class_B;
    public Int32 var; 

    private void setclassA()
    {
        _class_B._class_A.equals(this);
    }
}

public class class_B
{
    public class_A _class_A;        // I know this is null
    // code
}

Like I said I want to avoid instancing a new copy of class A because I want the values in class A to be set.

I've tried using a method to do it but still get a null reference.

Answer 1

Pass A in the constructor of B:

public class A
{
   private B _b;

   public A()
   {
       _b = new B(this);
   }
}

public class B
{
    private A _a;

    public B(A a)
    {
        _a = a;
    }
}

As mentioned in the comments you're completely misunderstanding .Equals(). It's used to compare whether two objects are equal not clone / pass references.