Compiler Warning (level 1) C4678

base class 'base_type' is less accessible than 'derived_type'

Remarks

A public type derives from a private type. If the public type is instantiated in a referenced assembly, members of the private base type will not be accessible.

C4678 is only reachable using the obsolete compiler option /clr:oldSyntax. It is an error when using /clr, to have a base class that is less accessible that its derived class.