How to delete the referenced object Completely?

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C#3.0

C#

Hi,
Here is my code:

class A
{
  Class B
  {
  }
}

Class C
{
  //stores the references of Class B
}

I am collecting the objects of A in a Dictionary. When I delete one of the object of A from dictionary then the corresponding B's object should also get deleted. But B's reference is not getting deleted.

Will you please tell how to accomplish this?