Class Dependency and Hierarchy
I'm quite challenged (read retarded) when it comes to understanding programming with classes. So far I've only written some very basic classes.

In VBA and VB6 I've often seen where ClassB can only become a valid object through a method of ClassA. For example, ADO Recordsets only become filled or usable through a method of the Connection object. A File object only becomes valid through the OpenFile method of a FileSystemObject object (never name your object object).

What theory governs this type of "structure" and what term is used to refer to this? I'm assuming this is something different from base classes and inheritance. Is this type of hierarchy something I'm likely to need to use when creating my own business logic and data access layer classes when database programming in .NET?
Class Dependency and Hierarchy
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I'm quite challenged (read retarded) when it comes to understanding programming with classes. So far I've only written some very basic classes.

In VBA and VB6 I've often seen where ClassB can only become a valid object through a method of ClassA. For example, ADO Recordsets only become filled or usable through a method of the Connection object. A File object only becomes valid through the OpenFile method of a FileSystemObject object (never name your object object).

What theory governs this type of "structure" and what term is used to refer to this? I'm assuming this is something different from base classes and inheritance. Is this type of hierarchy something I'm likely to need to use when creating my own business logic and data access layer classes when database programming in .NET?