7.5.1 Class Base Specification
A class declaration may include a base type specification that defines the direct base type of the class. If a class declaration has no explicit base type, the direct base type is implicitly Object. For example:
Class Base End Class Class Derived Inherits Base End Class
Classes may only derive from Object and classes. It is invalid for a class to derive from System.ValueType, System.Enum, System.Array, or System.Delegate.
Every class has exactly one direct base class, and circularity in derivation is prohibited. It is not possible to derive from a NotInheritable class, and the accessibility domain of the base class must be the same as or a superset of the accessibility domain of the class itself.
ClassBase ::= Inherits TypeName LineTerminator