Question

Considering the following case in C#:

class Foo
{
    public Foo() { }        
}

class Foo2
{
    private List<Foo> m_List = new List<Foo>();    
    public Foo2() { m_List.Add(new Foo); }    
}

Foo2 fooInstance = new Foo2();

Foo2 owns a List that contains a Foo – is there any built-in way for the Foo to figure out which List it’s contained in, and which object that list belongs to? In other words, can Foo obtain a reference to Foo2, or do I have to add an explicit backwards reference in Foo – pointing to Foo2 – as I’ve been doing?

Answer 1

Foo will have no knowledge that it is contained within a list unless you specify that somehow. A list after all is just a set of references to a location in memory. There is no relationship from a pointer to what contains the pointer.

class Foo
{
     public Foo2 Parent { get; protected set; }

     public Foo(Foo2 parent)
     {
         Parent = parent;
     }
}

class Foo2
{
      public Foo2()
      {
          List<Foo> x = new List<Foo>
          {
              new Foo(this)
          };
      }
}