C# Class Method passing reference

If I have a (C# VS2008) class (object) with fields and methods (A), and those method instanciate another object (B) which has fields and methods ... how do I reference the (A) fields/methods from within a (B) method? And what if a method in the (B) object instanciates another object (C) and wants to reference the (A) object fields/methods ... what is the proper syntax? For example:
class MyClassA
   int ItemAint;
   MyClassB CB = new MyClassB;
   public string MyMethodA1()
   { CB.DoItemB(???); }
   public string MyMethodA2()
   { // some stuff }
class MyClassB
   int itemBint;
   private string MyMethodB(???)
   { if ( ???.itemAint == 1 )
      { ???.MyMethodA2(); } }


I'm thinking this might work: (is it correct?)

class MyClassA
   int ItemAint;
   MyClassB CB = new MyClassB;
   public string MyMethodA1()
   { CB.DoItemB(this); }
   public string MyMethodA2()
   { // some stuff }
class MyClassB
   int itemBint;
   private string MyMethodB(MyClassA obj)
   { if ( obj.itemAint == 1 )
      { obj.MyMethodA2(); } }